Volume: Show safe media warning in settings.

If the safe media warning is enabled, make sure
we display it from the new inline slider preference in
Settings (without showing the volume dialog itself).

Also:
 - Update the warning dialog to the new sysui theme.
 - Separate the warning sentences with an additional line.
 - Fix the auto-dismiss timeout.
 - Add a system property to additionally enable the safe
   media warning for testing
 - Add more information to audio service dumpsys.

Bug:15434662
Change-Id: I95fec12c9049bbfdb7ebdf246160e4b12c0c5be3