Break out Bluetooth device icon from dashboard reference.

If a theme wants to use a different visual iconography style in
the subsettings, the bluetooth icon is shared between the dashboard
and that view. By adding this new reference, a themer can choose to
independently theme the subsettings version if their design calls
for that.

Change-Id: Iac3a58175f90357e0c42efe57b1e698d5c8e2ad3
Ticket: CYNGNOS-3176