[docs] Avoid including images from non-secure external HTTP sites

As discussed with @kaikreuzer earlier today:

Our website's host is reporting "mixed content" on some pages, meaning images served over HTTP while the site is HTTPS. This triggers nasty-looking warnings in browsers ("this content is not fully secure") and is generally bad practice.

Most of the culprits are READMEs in this repo:

10:23:22 AM: Mixed content detected in: /addons/bindings/anel1/index.html
10:23:27 AM: Mixed content detected in: /addons/bindings/dmx1/index.html
10:23:28 AM: Mixed content detected in: /addons/bindings/ekey1/index.html
10:23:28 AM: Mixed content detected in: /addons/bindings/enocean1/index.html
10:23:29 AM: Mixed content detected in: /addons/bindings/fritzaha1/index.html
10:23:30 AM: Mixed content detected in: /addons/bindings/frontiersiliconradio1/index.html
10:23:31 AM: Mixed content detected in: /addons/bindings/gc100ir1/index.html
10:23:32 AM: Mixed content detected in: /addons/bindings/homematic1/index.html
10:23:33 AM: Mixed content detected in: /addons/bindings/hue1/index.html
10:23:36 AM: Mixed content detected in: /addons/bindings/km2001/index.html
10:23:37 AM: Mixed content detected in: /addons/bindings/lcn1/index.html
10:23:40 AM: Mixed content detected in: /addons/bindings/milight/index.html
10:23:40 AM: Mixed content detected in: /addons/bindings/milight1/index.html
10:23:40 AM: Mixed content detected in: /addons/bindings/minecraft/index.html
10:23:41 AM: Mixed content detected in: /addons/bindings/nest1/index.html
10:23:42 AM: Mixed content detected in: /addons/bindings/netatmo1/index.html
10:23:43 AM: Mixed content detected in: /addons/bindings/nikobus1/index.html
10:23:45 AM: Mixed content detected in: /addons/bindings/opensprinkler1/index.html
10:23:52 AM: Finished processing build request in 4m14.601176527s
10:23:53 AM: Mixed content detected in: /addons/bindings/sonos1/index.html
10:23:58 AM: Mixed content detected in: /addons/bindings/xbmc1/index.html
10:24:00 AM: Mixed content detected in: /addons/bindings/zwave1/index.html
10:24:09 AM: Mixed content detected in: /docs/configuration/paperui.html
10:24:15 AM: Mixed content detected in: /docs/tutorial/uis.html

Suggestions on to resolve this:

Change the HTTP image link to an HTTPS one (this is acceptable)
If there's no HTTPS URL available for the image, migrate it in a doc folder under the bundle's root in the repository and reference it like so in the add-on's README.md; ![alt text](./doc/image.jpg).

FYI - Now the website build logs include the actual images that are problematic:

1:30:23 PM: Starting post processing
1:30:29 PM: Mixed content detected in: /addons/bindings/anel1/index.html
1:30:29 PM: --> insecure img urls:
1:30:29 PM:   - http://anel-elektronik.de/SITE/image/leisten/HUT-120.gif
1:30:29 PM:   - http://anel-elektronik.de/SITE/image/leisten/PRO-120.gif
1:30:29 PM:   - http://anel-elektronik.de/SITE/image/leisten/HOME-DE-120.gif
1:30:29 PM:   - http://img.youtube.com/vi/31ycP53jZVs/0.jpg
1:30:33 PM: Mixed content detected in: /addons/bindings/dmx1/index.html
1:30:33 PM: --> insecure img urls:
1:30:33 PM:   - http://img.youtube.com/vi/o0J4qyyfhio/0.jpg
1:30:35 PM: Mixed content detected in: /addons/bindings/ekey1/index.html
1:30:35 PM: --> insecure img urls:
1:30:35 PM:   - http://ekey.net/media/W/720/bilder/automatisierung/example_E.jpg
1:30:35 PM: Mixed content detected in: /addons/bindings/enocean1/index.html
1:30:35 PM: --> insecure img urls:
1:30:35 PM:   - http://img.youtube.com/vi/GpERJflmJKQ/0.jpg
1:30:36 PM: Mixed content detected in: /addons/bindings/fritzaha1/index.html
1:30:36 PM: --> insecure img urls:
1:30:36 PM:   - http://img.youtube.com/vi/qYrpPrLY868/0.jpg
1:30:37 PM: Mixed content detected in: /addons/bindings/frontiersiliconradio1/index.html
1:30:37 PM: --> insecure img urls:
1:30:37 PM:   - http://internetradio.medion.com/images/md87180_small.jpg
1:30:37 PM:   - http://internetradio.medion.com/images/md86988_small.jpg
1:30:37 PM:   - http://www.pinell.no/sitefiles/site8/shop/pinell-supersound-ii-white3.jpg
1:30:37 PM:   - http://revo.co.uk/assets/2013/10/H2_WNT_BLK_SUPERHERO2-486x395.jpg
1:30:37 PM:   - http://www.ruarkaudio.com/images/finishes-r2-walnut.jpg
1:30:37 PM: Mixed content detected in: /addons/bindings/gc100ir1/index.html
1:30:37 PM: --> insecure img urls:
1:30:37 PM:   - http://www.smarthome.com/media/catalog/product/8/1/8115big.jpg
1:30:37 PM:   - http://static.trustedreviews.com/94/8d9886/6e1c/7077-dendvd1940bk.jpg
1:30:37 PM:   - http://i0.wp.com/www.globalcache.com/wp-content/uploads/2009/10/iTachIP2IR-medtrans.png?resize=150%2C128
1:30:39 PM: Mixed content detected in: /addons/bindings/homematic1/index.html
1:30:39 PM: --> insecure img urls:
1:30:39 PM:   - http://img.youtube.com/vi/F0ImuuIPjYk/0.jpg
1:30:39 PM: Mixed content detected in: /addons/bindings/hue1/index.html
1:30:39 PM: --> insecure img urls:
1:30:39 PM:   - http://img.youtube.com/vi/Q4_LkXIRBWc/0.jpg
1:30:42 PM: Mixed content detected in: /addons/bindings/km2001/index.html
1:30:42 PM: --> insecure img urls:
1:30:42 PM:   - http://www.markinus.de/Openhab_Buderus.PNG
1:30:42 PM:   - http://www.markinus.de/Cometvisu_Buderus.PNG
1:30:43 PM: Mixed content detected in: /addons/bindings/lcn1/index.html
1:30:43 PM: --> insecure img urls:
1:30:43 PM:   - http://3.bp.blogspot.com/-d5mm3HC7uic/VpO2ctrfWNI/AAAAAAAAJOI/a37JMGhC4IY/s600/openhab_lcn.jpg
1:30:45 PM: Mixed content detected in: /addons/bindings/milight/index.html
1:30:45 PM: --> insecure img urls:
1:30:45 PM:   - http://img.youtube.com/vi/zNe9AkQbfmc/0.jpg
1:30:46 PM: Mixed content detected in: /addons/bindings/milight1/index.html
1:30:46 PM: --> insecure img urls:
1:30:46 PM:   - http://img.youtube.com/vi/zNe9AkQbfmc/0.jpg
1:30:46 PM: Mixed content detected in: /addons/bindings/minecraft/index.html
1:30:46 PM: --> insecure img urls:
1:30:46 PM:   - http://img.youtube.com/vi/TdvkTorzkXU/0.jpg
1:30:46 PM:   - http://img.youtube.com/vi/zAyNWmr7byE/0.jpg
1:30:47 PM: Mixed content detected in: /addons/bindings/nest1/index.html
1:30:47 PM: --> insecure img urls:
1:30:47 PM:   - http://watou.github.io/images/nest-binding-example.jpg
1:30:48 PM: Mixed content detected in: /addons/bindings/netatmo1/index.html
1:30:48 PM: --> insecure img urls:
1:30:48 PM:   - http://my.netatmo.com/img/my/app/module_int.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/battery_verylow.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/signal_verylow.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/wifi_low.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/module_ext.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/battery_low.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/signal_low.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/module_rain.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/battery_medium.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/signal_medium.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/wifi_high.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/battery_high.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/signal_high.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/wifi_full.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/battery_full.png
1:30:48 PM:   - http://my.netatmo.com/img/my/app/signal_full.png
1:30:49 PM: Mixed content detected in: /addons/bindings/nikobus1/index.html
1:30:49 PM: --> insecure img urls:
1:30:49 PM:   - http://img.youtube.com/vi/QiNb-8QxXpo/0.jpg
1:30:51 PM: Mixed content detected in: /addons/bindings/opensprinkler1/index.html
1:30:51 PM: --> insecure img urls:
1:30:51 PM:   - http://img.youtube.com/vi/lT0uxFlwu9s/hqdefault.jpg
1:30:57 PM: Mixed content detected in: /addons/bindings/sonos1/index.html
1:30:57 PM: --> insecure img urls:
1:30:57 PM:   - http://i.imgur.com/LKc2SjW.png
1:30:57 PM:   - http://i.imgur.com/2TTMTOg.png
1:31:02 PM: Mixed content detected in: /addons/bindings/xbmc1/index.html
1:31:02 PM: --> insecure img urls:
1:31:02 PM:   - http://img.youtube.com/vi/N7_5phTVbo0/0.jpg
1:31:03 PM: Mixed content detected in: /addons/bindings/zwave1/index.html
1:31:03 PM: --> insecure img urls:
1:31:03 PM:   - http://community-openhab-org.s3-eu-central-1.amazonaws.com/original/1X/63ec67c2a6dff6a42c8ef18e46333b0404953cb7.png
1:31:05 PM: Finished processing build request in 5m29.68304653s
1:31:12 PM: Mixed content detected in: /docs/configuration/paperui.html
1:31:12 PM: --> insecure img urls:
1:31:12 PM:   - http://img.youtube.com/vi/MV2a5qwtmRE/0.jpg
1:31:18 PM: Mixed content detected in: /docs/tutorial/uis.html
1:31:18 PM: --> insecure img urls:
1:31:18 PM:   - http://img.youtube.com/vi/MV2a5qwtmRE/0.jpg
1:31:26 PM: Post processing done

openhab / openhab1-addons

[docs] Avoid including images from non-secure external HTTP sites #5632