Nook camera stub (2/2)

Showing photospheres in Google+ on ovation (maybe hummingbird too)
causes an FC.  Log indicates that camera HAL is being queried.
Apparently USE_CAMERA_STUB is no longer sufficient, so this
implements a simple camera stub for g+.  Testing with other apps
that use the camera seems to have no ill effects or FC's
(verified via logcat).

Requires camera stub in device/bn/common.

Change-Id: Iaf9c52343dda6a2a70a13adffc175547e7b80e70