[fix bug 1054956] Refactor Firefox OS Get phone logic to remove JS dependency

Refactored "Get a Phone" logic on `/firefox/os/` and `/firefox/os/devices`, so users with JS disabled will get a full list of available phone partners/links in all countries (instead of just a link to the FAQ page). This should mean we now also have just a single list to maintain (in plain HTML :+1:). This will unblock [bug 1049042](https://bugzilla.mozilla.org/show_bug.cgi?id=1049042).

P.S - I also cleaned up some indentation in `get_devices.less` (adding `?w=1` to the PR URL might make review of this file easier).
@jpetto - One thing I'm undecided on is if this is too brittle on it's own in order to determine if a provider link is present? 

Perhaps it would more reliable/robust to check through a hard-coded array of values as before (comparing directly to `COUNTRY_CODE`), and then only if a match is found we then find the DOM element to call `show()`. Feels a little more reliable, as opposed to relying on DOM query matching alone. Thoughts?