Parsers with Error Recovery

@rupert, I just cloned your parser-recoverable repo and tried the Array example. Beautiful! Am going to study your code and see if I can use it to improve the MiniLaTeX parser. Should give better results than what I have now (chunking as above + error messages using Parser.Advanced).

I should be able to introduce parser-recoveralble gradually so as not to have to rewrite the whole parser before seeing benefits from it.