home: Ensure correct "incomplete installation" notifications are displayed

[gavofyork]

This refers to the home screen of Parity (127.0.0.1:8080/home/, home.parity). This ensure that the user does not get told to install any proxy when they could reasonably have our extension(s) look after it.

We need to know a few things:

• HAVE_PROXY: is home.parity functional? (i.e. is there a proxy in place somehow?)
• HAVE_EXT: is the extension installed?
• HAVE_CHROME: are we in the Chrome browser?
• HAVE_UGLYURL: are we using a 127.0.0.1:8080 URL?

Once in place, the logic is simple:

• (!HAVE_PROXY && HAVE_CHROME) || (HAVE_PROXY && !HAVE_EXT && HAVE_CHROME) => get-extension
• !HAVE_PROXY && !HAVE_CHROME => install-proxy
• HAVE_PROXY && HAVE_UGLY_URL => redirect

The actions based upon the logic are:

• get-extension: A notice is shown "Complete Parity integration is available for the Chrome browser. Click here for more information."; Clicking takes the user directly to the extension install page.
• install-proxy: A notice is shown "We do not yet have full integration for your chosen browser, but you can improve your Parity browsing experience by configuring a proxy. Click here for more information." Clicking shows the existing proxy-installation popup.
• redirect: The page is redirected to home.parity. In all other cases, no notices are shown.

[goldylucks]

@tomusdrw do we have an .parity endpoint to ping to test for proxy?

[tomusdrw]

On it's way: https://github.com/ethcore/parity/pull/1543

[goldylucks]

@tomusdrw I thought about wrapping Home and Topbar in a component that will manage the state for all this.

we r already using topbar as a 'kinda store', so maybe we'll do #16 first?