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/data/TaskInjectStorage.h

@@ -0,0 +1,29 @@
+#ifndef TASK_INJECT_STORAGE_H
+#define TASK_INJECT_STORAGE_H
+
+#include <vector>
+
+#include "utility/scheduling/Task.h"
+
+class Storage;
+
+class TaskInjectStorage
+	: public Task
+{
+public:
+	TaskInjectStorage(
+		std::shared_ptr<Storage> source,
+		std::shared_ptr<Storage> target
+	);
+
+private:
+	virtual void doEnter();
+	virtual TaskState doUpdate();
+	virtual void doExit();
+	virtual void doReset();
+
+	std::shared_ptr<Storage> m_source;
+	std::shared_ptr<Storage> m_target;
+};
+
+#endif // TASK_INJECT_STORAGE_H