logic: reimplemented task system to abort ast visiting

* reimplemented interrupting TaskParseCxx by adding a listener for the MessageInterruptTask and returning a failure status code on update. This cancels the parent sequence task which results in the indexed items not getting inserted into the persistent storage
* removed the capability for interrupting from TaskScheduler
* changed task system to be closer to the standard behavior tree implementation
* changed task system to accommodate the 3 status return types: Running, Success and Failure
* made TaskGroupSequential fail once a member task fails
* made TaskGroupParallel fail once a member task fails
* split TaskParse... into one task for indexing and one task for injecting
* added TaskRunner that handles updating and resetting the managed task
* fixed numbers that are shown as parsed file count in indexing ui
* fixed deadlock that originated from interaction between TaskScheduler and MessageQueue (one thread wanted to destroy a message listener on a task while the other one wanted to send as message as a task)

src/lib/utility/scheduling/TaskLambda.h

@@ -12,15 +12,12 @@ public:
 	TaskLambda(std::function<void()> func);
 	virtual ~TaskLambda();
 
-	virtual void enter();
-	virtual TaskState update();
-	virtual void exit();
-
-	virtual void interrupt();
-	virtual void revert();
-	virtual void abort();
-
 private:
+	virtual void doEnter();
+	virtual TaskState doUpdate();
+	virtual void doExit();
+	virtual void doReset();
+
 	std::function<void()> m_func;
 };