Change interface of BurstMediaItem to provide filepath.

- Instead of passing a byte array, use a file path for the burst media
item.
- Change the save operation in Stack saver to simply rename the image.
- The burst controller is now responsible for managing captured images and
implementations should free the captured images as soon as possible.

Change-Id: I6762972c68865d6ab15bd6fa20b60fb275f103f1
9 files changed