Caching the parsing of the muRascal library.

Parsing (and the first time around: also generating a parser for) the
concrete MuRascal library was a bottleneck for compilation (and hence
testing). When a pre-compiled version of the library exists and is
up-to-date that version is used, otherwise the library is parsed and
compiled as before (but now also saved for re-use!).
Sanitized the printed output of all compiler phases.