Add backup configuration action to Privacy settings

Settings now queries the backup manager for a configuration Intent and
text descriptive of the state of the currently-active transport.  These
are used by a new Intent PreferenceScreen within the backup section of
the Privacy settings UI.

When touched, the Configure item launches the Intent supplied by the
transport; when no such Intent is available, the item is disabled.  The
summary text describing the current backup state is also supplied by
the transport.

Bug: 2753632
Change-Id: I3d8fb3d4b08a2b6fa8d3ad8f9e02a66430948423
3 files changed