[BW]: [NIP] Preliminary changes needed to fix problems related to closing application while transferring messages. Still backend callbacking (application_delegate implementation) must be reimplemented, since backend notifications can be sent from another thread/fiber causing to (random) crash QT message loop.
Merge branch 'master' of https://github.com/InvictusInnovations/keyhotee
[BW]: [NIP] Introduced dedicated IGuiUpdateSink being thread safe - allows to deliver backend notification to the GUI always in the same thread, and avoiding this way QApplication::notify problems (usually it leads to infinite recursion).
[BW]: [NIP] Further changes related to checks against application close when transferring messages.
[BW]: [Ign] Small reformatting.