Remove MtpClient class from framework and public API

After reviewing this class I decided it would be best not to include it in the public API
since it adds no functionality that cannot be done using MtpDevice and other APIs directly.
So I am moving it to the CameraBrowser sample instead.

Also changed CameraBrowser to build against the SDK to ensure all the necessary APIs for
PTP support have been made public.

Bug: 4067029

Change-Id: I585b06104084953176d018ced08bba0cb4607490
Signed-off-by: Mike Lockwood <lockwood@android.com>