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/utility/messaging/MessageBase.h

@@ -19,6 +19,7 @@ public:
 		: undoRedoType(UNDOTYPE_NORMAL)
 		, m_sendAsTask(true)
 		, m_keepContent(false)
+		, m_cancelled(false)
 	{
 	}
 
@@ -59,6 +60,16 @@ public:
 		return m_keepContent;
 	}
 
+	void cancel()
+	{
+		m_cancelled = true;
+	}
+
+	bool cancelled()
+	{
+		return m_cancelled;
+	}
+
 	virtual void print(std::ostream& os) const = 0;
 
 	std::string str() const
@@ -74,6 +85,7 @@ public:
 private:
 	bool m_sendAsTask;
 	bool m_keepContent;
+	bool m_cancelled;
 };
 
 #endif // MESSAGE_BASE_H

src/lib/utility/messaging/MessageQueue.cpp

@@ -241,6 +241,11 @@ void MessageQueue::sendMessage(std::shared_ptr<MessageBase> message)
 			listener->handleMessageBase(message.get());
 			m_listenersMutex.lock();
 		}
+
+		if (message->cancelled())
+		{
+			break;
+		}
 	}
 }
 
@@ -260,7 +265,7 @@ void MessageQueue::sendMessageAsTask(std::shared_ptr<MessageBase> message, bool
 				[listenerId, message]()
 				{
 					MessageListenerBase* listener = MessageQueue::getInstance()->getListenerById(listenerId);
-					if (listener)
+					if (listener && !message->cancelled())
 					{
 						listener->handleMessageBase(message.get());
 					}