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