Emit service discovery error during internal device discovery

This was discovered when starting a service discovery while no
Bluetooth device is connected.

Change-Id: Ibb970ee6cb95ff50bca635813cce23c4d7f8e3c6
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Remove private and unused API from QBluetoothServiceInfoPrivate

Presumably this API was intended to update attributes while the service
info object is already registered. It was not implemented anywhere. No
reason to keep it.

Some minor documentation fixes

Change-Id: If6b4b7c37d99027d49a7af48c282725228e9a6c7
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>