Create a grammar library that works on CF grammars

[LPeter1997]

The current parser library is kind of messy because it attempts to work on a semi-eBNF notation but also tries to shove in CF transformations, all while emitting a recursive-descent parser. I have privately worked on a grammar library that should be integrated. It would work with CF languages, but eBNF notation could also be turned into it. It would also open up the possibility for other parsing strategies (LR, GLR, LL, ...).