Point to Point Constraint, Shape Restriction Framework

Point to point constraint code was done. The code is still far from perfect (it have some bugs that seem to appear like a random jumping around the area, so may be a logic point).

Even the constraint is important as constraints were introduced and they can make NaroCAD a more than useful tool by supporting a lot of operations, sometimes the problem is that a lot of testing and crashes are just because of incompatible operation of different objects. For example you should not apply a constraint like: Line Length Constraint on a circle shape. You should apply it only on a line. Because of this the code behind was extended to support for references on your operations at two levels:
- a logical (high level) one, like: you can pick the reference shapes and the operation that applies to
- a reference based (low level) like: you can write your custom code to accept/exclude a shape from candidates
Also this works as previously code for shapes that you don't want that this extra checks to occur.

I will try to work in two directions: try to integrate this work to actions/meta-actions to use explicitly this code to give to user information like: "Incompatible shape to this operation".
This will be nice to avoid known crashes of NaroCAD code or of OpenCascade operations.

You may check it using the nightly build.