Add more MediaStore constants for playback intents

Constants are derived from this doc:
https://docs.google.com/a/google.com/document/d/1lmlFcTeefLDRp_bpMrXk3yK9nKxoTVfpcShanpLxiMg/edit#heading=h.b16863tyyjzv

That doc contains the full explanation of these changes.

I'm making this change on behalf of {elmas,pengr} who don't have
android source access but designed this in collaboration with
rharagutchi on the play music team. I'll probably have to route any
significant questions through them.

Bug: 12874557
Change-Id: I85a4bee57a2bde519da0dc6de2cad9d036da225c