removes move checking code from Squares and renames it to Square
adds commented move checking code to Board and updates it to use new Colour module
corrects reference to Square module in Board
starts implementing Piece value objects - much unfinished

Piece.NONE has been dropped in favour of just using nulls.

Fen and Piece require each other at the moment.  probably
best to hardcode FEN codes into Piece instead of messing
around with mappings between the two.  Fen representation
is good enough anyway.
adds files which should have been in previous commit

also the previous commit should have mentioned that the Chess module
was dropped.  It only had a few move checking utilities left in it and
they were moved to Board and put in comments for sorting out later.