removes square, file/rank, coords and algebraic square utilities from Chess

this breaks things; anything that breaks as a result should start using the new
Square value objects once they're done.
adds Squares module - a collection of objects representing the squares
with methods for retrieving and enumerating the squares.

Any references to squares should now be referring to these objects.  Equality
and identity comparison will still work - the constructor is closed off so there
will be exactly 64 Squares in existence, one for each square of the chessboard.