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/Storage.h

@@ -2,6 +2,7 @@
 #define STORAGE_H
 
 #include <functional>
+#include <mutex>
 #include <string>
 
 #include "data/name/NameHierarchy.h"
@@ -32,9 +33,13 @@ public:
 	virtual void forEachCommentLocation(std::function<void(const StorageCommentLocation& /*data*/)> callback) const = 0;
 	virtual void forEachError(std::function<void(const StorageError& /*data*/)> callback) const = 0;
 
+	void inject(Storage* injected);
+
+private:
 	virtual void startInjection();
 	virtual void finishInjection();
-	void inject(Storage* injected);
+
+	std::mutex m_dataMutex;
 };
 
 #endif // STORAGE_H