Let Betza parser understand extended atoms for larger leaps

Let Betza parser understand extended atoms for larger leaps

The Betza parser now understand an X suffix to an atom as a 3-square
extension in the long direction, and an Y suffix as a 2-square extension
in both the long and short direction. E.g. FX for a (4,1) leap, NY for
a (4,3) leap. This allows leaps of up to (6,3) = GX and (5,5) = GY.