WIP

I'm trying to return consistently-formatted strings when a method asks
for "moves" vs "spaces".

Starting on this refactoring made me realize how much other refactoring
could be done.  I think most classes can be made to look like ForPawn,
where they instantiate themselves and avoid passing 3-4 args to each
method.  That will hopefully fix the current error...
Finish refactoring moves
More Utils
Merge branch 'refactor_moves'

Still not perfect, but good enough for now.  I'll probably refactor more when I
add en passant and pawn promotion.