QBluetoothDeviceInfo - add "non-addressable" devices support

On OS X and iOS CoreBluetooth hides addresses from a user, providing
NSUUID (similar to uuid, by generated by Apple) to identify devices ("peripherals").
Since we still must be able to somehow "address" these devices later,
we use these (unique) uuids instead of addresses for LE devices:
add a data-member, setter/getter/ctor + update operators '=' and '=='.

Change-Id: I74b73c1413d7014e04cbfda6cef501defa15ed8e
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>