#39 Update Netlify CMS

[Quicksaver]

• [x] Closes #39 - Updates Netlify CMS to 1.0.2
• [x] Closes #47 - Implement a language filter (backport from Uhub).

Notable Netlify CMS changes

Full list of changes at https://github.com/netlify/netlify-cms/releases (previous version was 0.4.6)

0.5

• Extra blocks in markup editor: code, quotes, lists; only basic styling applied
  • Modified Blog post 3 to contain all the available markup blocks
• Authentication with Git Gateway and Netlify Identity, editors don't need their own Github account to use the CMS
  • It's not working very well yet. For instance, I can login but it never directs me to the CMS interface. Login with services (Github, Google, etc) doesn't work at all as it always redirects to the homepage.
  • https://www.netlifycms.org/docs/add-to-your-site/#authentication
  • https://www.netlify.com/docs/identity/

    0.6

• React 16
• Better field validation errors in the editor; when a required field is empty, it's made much more clear, both in the message over the field, and with a pop up notification at the top of the screen! Nested fields, such as those inside of an object or list, are still not validated.
• Removed IE11 support

  0.7

• Media library UI for browsing, adding, and removing media from your content repo!
  • The library shows assets in from the directory set as media_library in the CMS config.
• Add delete: false config option to disable deletion for a collection
• Add scroll sync toggle to editor

  1.0

• New UI!
• Content deletion works in editorial workflow
• Descriptions can now be added for each collection.
  • Added sample descriptions to each content type.

[Quicksaver]

@pdsdesign can you check my markdown.scss file and see if it's following our accepted standards and layout and stuff? And this PR isn't likely to be merged for a few weeks, so if one of these days you're feeling creatively inspired, feel free to style the those extra markdown blocks to fit better with the Besugo theme directly in this branch, although as we discussed before that's not strictly necessary since every project will need its own taste of custom styling. 😄