Detect added files

[mcserep]

During incremental parsing, new added files should be detected. There are 3 possible solutions:

1. Not detecting added files, since parsing will detect and parse them by analyzing the build commands. (Investigate whether this is a valid issue, is this information really unimportant for other tasks too?)
2. Detect new files via filesystem parsing. Drawbacks: files not included in the compilations process might be detected; and the source code path prefix must be known (e.g. by a console parameter).
3. Detect new files via the build commands. In this case the compilation database should be already built for the incremental parsing file change detection (currently done in the worker() method), so some refactoring is required.