Overlay updates

* Enable install non market apps
* Disable touch/lockscreen audio
* Disable haptic feedback

* Disable homescreen scrolling wallpaper
Hammerhead: enable echo cancellation for voice communication

This greatly improves the quality of VoIP calls, tested on the app
"LINE". Without this, the other party will be able to hear echo
of their own voice.

Reference:
http://source.android.com/devices/audio_implement.html#preprocessing