ochre-lang

Copperbox revision 3197.

I've fixed a long standing bug in trait flattening where trait composition was not finding the "combined difference" of two traits instead it was only finding the difference of the left trait (as per the difference operator on Haskell's Data.Map).

Also, I've made the compiler write to file as the final step rather than write to debug. Implementing this makes Ochre seem like a real compiler.