Camera: Adds support for meta data callbacks

- This change adds a new type of callback
  that will be called when there are pending
  meta data notifications.

Change-Id: I190971b2d0d4d189e8f4edee8204ef65b62cd453
Cherrypicked from 9706034f16d23f96966dbd060f1bb85c5a4d976a

Conflicts:
	core/jni/android_hardware_Camera.cpp