Refactor the remote hotkeys to avoid round trips

The previous implementation was hard to follow and maintain. Instead of
doing intentional rounds trips, we use now a two way approach. GUI is
automatically forwarding remote actions by calling "callHotkeyActionRemotely"
through DBus. Core on the other hand, emits a signal "remoteHotkeyAction"
that is processed in a different function in GUI.
On both sides, actions from the same local machine are filtered.

ref T402

src/blackcore/inputmanager.h

@@ -85,7 +85,7 @@ namespace BlackCore
         void setForwarding(bool enabled) { m_actionRelayingEnabled = enabled; }
 
         //! Call functions by hotkeyfunction
-        void callFunctionsBy(const QString &action, bool isKeyDown);
+        void callFunctionsBy(const QString &action, bool isKeyDown, bool shouldEmit = true);
 
         //! Triggers a key event manually and calls the registered functions.
         void triggerKey(const BlackMisc::Input::CHotkeyCombination &combination, bool isPressed);