Launcher: Add hotword detection

PS1: Added static hotwords detection for voice search, similar
to the Google Now Launcher. By saying "ok google" or "hey google",
Voice Search will start.

PS2: Cleaned up recognizer restart logic and unneeded code

PS3: Added configuration in the settings fragment, fixed a crash when
turning the launcher in landscape when in Settings

PS4: Now listening to custom hotwords :)
Demo video: http://youtu.be/SFv4P_1VTfo

PS5: Fixed crash on pause when no hotwords were setup

PS6: Fixed hotword enable checkbox not working

PS7: Muted the beep-beep, not without consequences as Google are
stupid enough to put that stupid beep-beep on STREAM_MUSIC, cutting
off currently playing music when we mute the stream. Added
a checkbox to disable voice recognition if music is playing.

PS8: Turned off debug flag, ship it

PS9: Whitespaces cleanup

PS10: More cleanup, added NEW_TASK flag, unmute audio when
leaving the launcher

Change-Id: I55f0a4e607b24054105c81e8dfed7fe5bbaa9916