Path argument is now used to read files.
AppController now throws AbortProgramException to end.

+AbortProgramException class (holds an exit code).
Pulled the argument parsing into GetRunSettings method.
Fixing up broken tests.

No longer asserts exit codes; AppController now signals non-success exits via AbortProgramException.
Adding Setups() for ArgumentParser to return RunSettings, since AppController now uses its Path.