error messages are not helpfull

[MARTIMM]

As you've mentioned before, the error messages lack the information needed to find the problem. So I thought I make it an issue. Above all that, quite a few of those messages cannot be properly encoded in json. I noticed things like \n, single \ and " in those strings.

[CurtTilmes]

Yes, I've learned a lot about Grammars since the initial implementation. I'd like to do a complete overhaul when I get a chance. Complete error messages will be a lot of work, but it needs to get done.