Code optimisation.
opacity removed since included in std colors.
code refactoring
The abstract shape factory is now a singleton.
code simplification
rx and ry operations removed from IEllipse
getIntersection removed from IEllipse
Implementing dot mirroring
code refactoring
getRadius in ICircleArc removed
Improving the model definition by fixing a Refused Bequest anti-pattern
for freehand shapes
Separating std grid interfaces