[bluez-qt] Fix updateAudioProperty return type
[bluez-qt] Add default Authorize() implementation and allow asynchronous reply

By default, if the remote device is not paired, Authorize() will now
return an error. If it is paired but not trusted, the agent will
invoke requestAuthorization() and allow an asynchronous reply via
replyRequestAuthorization().
[bluez-qt] Make org.bluez.Device.GetProperties() call asynchronous
Merge pull request #9 from blammit/authorize-async

Add default Authorize() implementation and allow asynchronous reply