methodDcl/methodMod & added statement rule

- 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`