Fix a glaring out of bouds error in MoveBuider's List()
Add `MoveBuilder.flip()` which reverses transformations

This lets us scan an entire horizontal or vertical line without having to write
transformations twice - write once and call flip(), instead.
Remove defunct "NUMBER" token type
Add a `listMoves` method to Piece.Base

This takes all moves from findPossibelMoves() and converts it into an array of
strings needed for the list command.
Initial implementation of MoveBuilder for all pieces bar Knights

Damn knights...