[android] Add Android TV support

Add Android TV support. This simply means adding an entry to the TV
launcher.

Tested on ADT-1 Android TV device.

Video playback seems to work fine, audio playbacks work with stereo
PCM and basic passthrough. A separate commit adds 5.1 PCM support.

There are two significant issues that I saw:
- crash on exit, looks like double free at /system/lib/libmedia.so
  (android::sp<android::AudioTrackClientProxy>::~sp()+10),
  maybe something to do with threading? or just an Android bug...
- a warning flood on playback of many videos:
  W/art: Attempt to remove local handle scope entry from IRT, ignoring

Both of these look like either general issues introduced with Android L
and/or ART, not Android TV specific issues (but I did not confirm that).
[android] Declare touchscreen as unneeded

We do not require touchscreen (though we can use it). Declare it as not
required in the manifest (it defaults to required as per documentation).

This is mostly cosmetic at this point, since it mostly affects Play
Store filtering, but it does not hurt to have the manifest correct.
Merge pull request #5083 from anssih/android/tv

[android] Initial Android TV support