camera: Allow devices to load custom CameraParameter code

* Some devices need additional code to load their cameras. Add a hook
  for extra classes and symbols to be included.

Originally implemented in Android.mk at 38b27bf2e5079441358288402b38865ba7c1d9d6
Credit to Ethan Chen for original Android.mk implementation

Change-Id: Iec667af2f0bfdb41f14df342cb128908244d7af0