1. There has been implemented calculation of all possible types of continuity for shared edges:
* G1 is set if tangential planes are the same for connected faces in each control points through the edge;
* C1 is set in addition to G1 conditions if derivatives, orthogonal to the edge on each face, are equal vectors;
* G2 is set in addition to G1 if the centers of principal curvatures are the same for connected faces in each control points through the edge;
* C2 is set in addition to C1 and G2 if directions of principal curvatures are equal;
* CN continuity is set only if both connected faces are based on elementary surfaces (the conditions for this case are similar to C2 continuity).
2. ShapeFix::EncodeRegularity() is merged into BRepLib::EncodeRegularity().
3. Implemented several test cases to check correct handling of regularity.
4. Fix incorrect usage of BRepLib::EncodeRegularity() in BRepBuilderAPI_Sewing.
5. Implement a method for calculation of regularity on the given list of edges.
6. Documentation updates
