Service discovery via Bluez5

At the same time we shift the ServiceClassUUID to service name mapping
to QBluetoothUuid. It was used by Android and now Bluez 5 uses it too.

Task-number: QTBUG-32085
Change-Id: I9f2d4dc4e2997683485f2ba7aaefb646cb72fb75
Reviewed-by: Aaron McCarthy <mccarthy.aaron@gmail.com>
Bluez5: Ensure device discovery returns meaningfull RSSI data

If the discovery process was started by QBluetoothDeviceDiscoveryAgent
and Bluez wasn't already in discovery mode then the RSSI values
are 0. The retrieval of RSSI data takes a bit more time.

To find a compromise between speedy return of device scan information
and the delayed RSSI information we continue to monitor the device scan
and update RSSI information as the values are propagated by Bluez.
However the deviceDiscovered() signal is not emitted again  after an
update. Only re-calling discoveredDevices() will return the most
up-to-date RSSI values.

Task-number: QTBUG-32085
Change-Id: Icb6566d51503a6004fa3f25c499fc7f941bd7fee
Reviewed-by: Aaron McCarthy <mccarthy.aaron@gmail.com>