0028605: Improve the algorithm of calculation of valid intersection range of an edge

0028605: Improve the algorithm of calculation of valid intersection range of an edge

- New method BRepLib::FindValidRange() has been added. It computes the range of the edge not covered by boundary vertices.
- The algorithm of calculation of valid intersection range in the class IntTools_ShrunkRange has been corrected to use the new method.
- The method BOPTools_AlgoTools::MakeSplitEdge() has been improved to protect against errors in the case of reversed orientation of the input edge.
- Two new Draw commands have been added:
  validrange - it calls the new method BRepLib::FindValidRange().
  tolsphere  - it shows tolerances of vertices by drawing a sphere around each vertex of the shape.
- The test cases "offset shape_type_i_c YE1,YE2" became better. The scripts have been corrected to reflect the new state.