trying to do imports and failing, added grammer for classes and started on sem check
trying to do classes
Merge branch 'lukesextensions' of https://gitlab.doc.ic.ac.uk/lab1314/wacc_37 into extensions
Things that luke did on my computer to do with classes
semantic checks for classes almost done, except method checks for a valid function
fixed error relating to undefined class methods
classes can (semantically) have fields of other classes now
can construct classes of the other classes in a class (semantically at least)
Types are now in semantic checker and backend.
Added type subset hierarchy.
Small StringUtils refactoring.
Working on signed values of binary literals.