Rough implementation of lockscreen playback controls. Notes:
* currently uses the Settings API, since the inter-app comms API hasn't landed yet
* lockscreen UI is still very ugly (waiting on final specs)
Mostly prettify the lockscreen media controls. Still needs:
* Fixing the elastic
* Album art
* Hide the controls when appropriate
Show and hide the lockscreen media controls as appropriate
Fix some sliding stuff (I am cargo-culting this...)
Keep the elastic animation from firing on the lockscreen when the media controls are visible