Moves iterating over OrbitIter into PointGen class. Now need to add
hyperbolic implementation.

Signed-off-by: John Lawson <john@jwlawson.co.uk>
Merge remote-tracking branch 'origin/master'
Tidies up so Tiling now uses PointHandler interface and adds abstract
SquareCanvasHolder to contain common code from Focal and Tiling.

Signed-off-by: John Lawson <john@jwlawson.co.uk>
Fixes problem with drawing.

Signed-off-by: John Lawson <john@jwlawson.co.uk>