Add Remote Key Listeners for Firefox OS TV

[darkwing]

This game could easily be ported to Firefox OS TV by adding/updating a few key listeners

https://developer.mozilla.org/en-US/docs/Mozilla/Firefox_OS/TVs_connected_devices/TV_remote_control_navigation

https://developer.mozilla.org/en-US/docs/Mozilla/Firefox_OS/Platform/Keyboard_events_across_browser_elements

I have a Firefox OS TV so I can test things out for you! :)

[getify]

So far in @darkwing's testing, the "1", "2", and "3" work on the remote on the main screen... then there's some other bug that crashes the game it seems.

Other events issues to address:

• the current keyboard handling assumes needing <space> to fly up... need an additional key binding that would make sense on the tv remote... wondering what that should be? <up>? <ok>?
• need to figure out if "exit" on the tv remote appropriately maps to <escape>? and how do we get "exit"?
• need to figure out if "ok" on the tv remote appropriately maps to <enter>?