[Grace-core] Some comments from Tijs on parsing Grace

[James Noble]

so, somehow, sometime soon, we should try to get Tijs, Michel, & whoever else to see if we can come up with a draft... J 

> I’ve independently come to the same conclusion.  For example, I’ve been confused (in switching from old to new class syntax) when I accidentally put a method inside a method; the parser isn;t looking for the method keyword, so you get a confusing message.  The grammar would be simpler and the error messages better if the parser just accepted it, and then there was a structural check along with the other checks on the parse tree.