Did a bit of cleaning up in grammar.
- Including renaming rules as follows:
  - *multiArgMessageNoPar* => *multiKeyMessage*
  - *singleArgMessageNoPar* => *singleKeyMessage*
  - *binaryMessageOperand* => *binaryMessagearg*
- Including renaming misc. builder methods in ANTLRToAST
  - append* => *Builder
  - append* => *BuilderFromReceiver

Signed-off-by: Jakob Brandsborg Ehmsen <jakobehmsen.github@gmail.com>