Add "Manage backup data" item to "Backup & Reset" settings.

This patch uses new IBackupManager API. Item's label is taken from
getDataManagementLabel and Item's action is taken from getDataManagementIntent.
If getDataManagementIntent is null (or backup service is unresponsive)
the item is not displayed.

Change-Id: I19cbf7fa625fccff751f923aa41b7d64ccb6c1d3