ui, logic: design for license ui and forcing the user to enter a key on first open

This change integrates the license key ui into the application and makes it necessary for the user to enter a correct
key. The check for a correct key is done on startup and whenever a project is loaded. The check for the key also
includes a check whether the location of the application has changed.

src/lib_gui/qt/window/QtMainWindow.h

@@ -83,6 +83,8 @@ public:
 	void loadLayout();
 	void saveLayout();
 
+	void forceEnterLicense();
+
 protected:
 	bool event(QEvent* event);
 	void keyPressEvent(QKeyEvent* event);
@@ -92,6 +94,8 @@ public slots:
 	void popWindow();
 	void clearWindows();
 
+	void activateWindow();
+
 	void about();
 	void openSettings();
 	void showLicenses();