- can now successfully check that class has at least one constructor
- added rule fixing `this.x = 123;` in `J1_publicfields.java`
- cleaned up Test.py a bit more

- added AstBuilding.py
- new AstNodes.py that stores all Nodes and different types that we'll
create
- cleaned up Parsing.py heavily, now returns the parse tree
- cleaned up Test.py as best I could to accomodate everyone
- removed not needed file utils.py
- commented out my code in Weeding.py

changed cfg to handle error cases: array intialize to empty brackets, and clean up cfg for methodmod

- casts & castExprType
- instanceof
- method and field invocs
- params separated by commas
- public abstract class

Need to git pull the latest CFG

- added new methodOrField thing that lets you invoc methods and fields
recursively infinitely
- statement can now declare and define any type
- removed arrayID nonterminal
- adjusted arrayAccess because of arrayID removal
- added a cmd in README to make my workflow more convenient
- commented out all the many many many prints in Test.py

Made changes to scanner and grammar after going over around 3/4 of error public test cases. (e.g. bitwise operations, integer range checking)

- methodDcl is now one rule (rather than splitting into
abstractMethodDcl & normalMethodDcl) had to do this because they were
too similar, getting conflicts as abstractMethodDcl ends with SEMICO and
normalMethodDcl ends with methodBody which has a rule `methodBody
SEMICO`
- added rule `statement primitiveType variableDcl SEMICO` because we
didn't have a way to parse 'int x = 0;' or similars, it should actually
be `statement type variableDcl SEMICO` but that causes conflicts in the
grammer with `arrayAccess`

- condensed getting the last rule, no more need for copying the stack
- children are now right way round, not reversed