Adds 4 new Settings:
Secure.MOUNT_PLAY_NOTIFICATION_SND - Play notification sound on events
Secure.MOUNT_UMS_AUTOSTART - Auto-start UMS when host detected
Secure.MOUNT_UMS_PROMPT - Show notification when host detected
Secure.MOUNT_UMS_NOTIFY_ENABLED - Show notification while UMS enabled
These settings are also added to the Settings backup list
Signed-off-by: San Mehat <san@google.com>