* 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.