Bug fixing

Continued fixing bugs 4-8 bugs a day. Fixed bugs related to Fillet2D, Fillet 3D, Property Grid, Tree View, Ellipse crash, Cut, shape intersection algorithm.

As main directions that remained to be fixed are:
- the Undo Redo still needs fixing,
- the magic points needs improvements so that the solver detects edges and surfaces (improvements are needed especially at curves like arc, surfaces like cylindrical),
- because of the parametric propagation a node that references another node (like Extrude is referring a Rectangle node) is using a hidden node named SubShape node that describes the referenced node. We have to find and implement a guideline to establish when a node that references another node should hide the target. Ex: Extrude when applied on a rectangle should hide the referenced rectangle, when applied on the face of another Extrude should not hide it.

Currently in the bug list there are 12 more bugs and 7 bugs with enhancement priority (the enhancements will be not closed for this beta release). Closed around 49 bugs.