Bug 1094094 - [Stingray] Implement navigation and contextmenu of Apps Deck

1. Enable app launch in app-deck
2. refine styling based on UI/UX spec (though it is not completed yet)
3. l10n work of app-deck
4. refer to the patch of bug 1098274, add 'pin to home' functionality
OK, I could make comment about this in `tv_apps/app-deck/js/context_menu.js`. However, the original code of getting screenshot is already recorded in https://bugzilla.mozilla.org/show_bug.cgi?id=1100238 and https://github.com/mozilla-b2g/gaia/pull/26315