Removing Generics (arguably simpler).
De-lint: unneeded parens

Signed-off-by: Leo C. Stein <leo.stein@gmail.com>
Comments only.

Signed-off-by: Leo C. Stein <leo.stein@gmail.com>
Slightly more compact printing (group same-color
moves together in output)

Signed-off-by: Leo C. Stein <leo.stein@gmail.com>
"Simplified" printing by use of zip, map, intercalate.

Signed-off-by: Leo C. Stein <leo.stein@gmail.com>
Now including Box in Board. Simplified loading of levels at the same time.
Big speedup by filtering possibilities:
only consider states where the squares are all within
a bounding box which includes everything on the
board plus the number of squares.