Add a theme for setup and/or form style input for TV/leanback

Theme initially adds customized text appearances that should work
better in the leanback environment. Device makers could modify the
theme and then apps participating in the device setup experience
can all use this theme for those activities to provide a more
cohesive user experience during the setup process.

Bug: 16223105
Change-Id: I3d9f83e29ddce2a0a4e6b501d01a7365c1d11b5b