fixed calling io_service::poll_one(); processes a handler, so call to run_one() unnecessary and may lock up thread
reordered source device and remote release control objects to properly destroy them
don't set default release settings in OnDestroy() to prevent lockup
pass SourceDevice shared_ptr to RemoteReleaseControlImpl to prevent lockup when calling EdsCloseSession() too early
added comments to AsyncReleaseControlThread class
removed the Bug entry just fixed from TODO.txt
added EnableUpdate() method
implemented reusing active viewfinder as "mirror lockup" on HDR photo mode; prevents lockups
fixed crashes in async version of Release() when no focus could be found, or other error occured
fixed bug when clicking on Connect when already connected to a camera (lockup in EdsCloseSession())