logic: improved indexer parallelization

* added task that injects into PersistentStorage parallel to indexer tasks.
* added Blackboard for Task classes

src/lib/data/StorageProvider.h

@@ -0,0 +1,26 @@
+#ifndef STORAGE_PROVIDER_H
+#define STORAGE_PROVIDER_H
+
+#include <memory>
+#include <mutex>
+#include <list>
+#include "data/IntermediateStorage.h"
+
+class StorageProvider
+{
+public:
+	int getStorageCount() const;
+	void pushIndexerTarget(std::shared_ptr<IntermediateStorage> storage);
+
+	// always returns a usable storage
+	std::shared_ptr<IntermediateStorage> popIndexerTarget();
+
+	// returns empty shared_ptr if no storages available
+	std::shared_ptr<IntermediateStorage> popInjectionSource();
+
+private:
+	std::list<std::shared_ptr<IntermediateStorage>> m_storages; // larger storages are in front
+	mutable std::mutex m_storagesMutex;
+};
+
+#endif // STORAGE_PROVIDER_H