logic: File Manager

* added FileManager that keeps track of the files analyzed by the project. It therefore checks if files get added, updated or deleted from the source- and include folders.
* refactored ASTVisitor::hasValidLocation() and implemented one version that search for the location in the currently parsed file and one that searches in all the project's source files.
* quickfix: switched order in FileManager so that header files are parsed first.
* created folder for helper classes used in tests.
* added test code for FileManager
* adjusted test code for Parser Tests.

src/lib/utility/file/FileSystem.h

@@ -0,0 +1,34 @@
+#ifndef FILE_SYSTEM_H
+#define FILE_SYSTEM_H
+
+#include <string>
+#include <vector>
+
+#include "utility/file/FileInfo.h"
+
+class FileSystem
+{
+public:
+	static std::vector<std::string> getFileNamesFromDirectory(
+		const std::string& path, const std::vector<std::string>& extensions);
+	static std::vector<std::string> getFileNamesFromDirectoryUpdatedAfter(
+		const std::string& path, const std::vector<std::string>& extensions, const std::string& timeString);
+
+	static std::vector<FileInfo> getFileInfosFromDirectoryPaths(
+		const std::vector<std::string>& directoryPaths, const std::vector<std::string>& fileExtensions);
+
+	static std::string getTimeStringNow();
+
+	static bool exists(const std::string& path);
+	static std::string fileName(const std::string& path);
+	static std::string extension(const std::string& path);
+	static std::string filePathWithoutExtension(const std::string& path);
+	static std::string absoluteFilePath(const std::string& path);
+
+	static bool equivalent(const std::string& pathA, const std::string& pathB);
+
+private:
+	static bool isValidExtension(const std::string& filepath, const std::vector<std::string>& extensions);
+};
+
+#endif // FILE_SYSTEM_H