Simplify QBluetoothTransferManager code.

QBluetoothTransferManager implementation is very simple. There is no
need for three individual files.

Change-Id: Ia205f96c4b59366f6b9613a7b45f2836a93a03e6
Reviewed-by: Fabian Bumberger <fbumberger@rim.com>
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
QNX: Fix compilation and a compiler warning

Change-Id: Id3de289238013edfc9737f444d3db95be3bd761b
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Refactor device and service discovery errors

- Make them more consistent with other Qt modules
- Propagate the error during device discovery to the QBluetoothServiceDiscoveryAgent

Change-Id: Idcd3e0e6061b85e8b6adad248625740f3b91289a
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>