App data backup security policy.

Policy covers:

 * backup_data_file type for labeling all
   files/dirs under /data dealing with
   backup mechanism.

 * cache_backup_file type for labeling all
   files/dirs under /cache dealing with
   backup mechanism. This also covers the
   the use of LocalTransport for local archive
   and restore testing.

 * the use of 'adb shell bmgr' to initiate
   backup mechanism from shell.

 * the use of 'adb backup/restore' to archive
   and restore the device's data.

Change-Id: I700a92d8addb9bb91474bc07ca4bb71eb4fc840e
Signed-off-by: rpcraig <rpcraig@tycho.ncsc.mil>