Camera button support (1/2)

Add new bitmask for Camera button and "hasCamera" boolean.
For those devices that have dedicated Camera key
(like Sony ZL/ZR/Z1/...)
Change-Id: I1a6681664f9f3fd3f30221ba10b082cb5f8cafca

Camera button support: make it actually work
Previous commits were merged so fast that I didn't even
added the code that actually DOES launch the camera.
Let me fix that.
Change-Id: I4fcb3c46e5fd50e273dcf19fd3eb35a3f9d979e0

Camera button support: useful features & bugfixes (1/2)
Screw the remapping, let's make something more useful!
Replaced the code to actually launch Camera app, not just fire the shutter.
I won't remove it: it's cool to have an option to double-click Home for Camera.
Added:
  * Camera wake (with button half-press) and unlock options
  * "Peek": releasing the half-pressed Camera button will
    turn the screen back off
  * Camera playback control

Change-Id: Id49e09e20d81cd80d9800ab8ab0f200d44485a09
Remove 'Allow custom buttons' checkbox (1/2)

Let hardware buttons be rebound by default.

Change-Id: Ib4fcae7d93dc63d53490442d7ff44678583b0d9c