[GeoLib] Method for computing all intersec. pnts between 2 plys.
[FileIO/GMSHInterface] Compute/add all intersec. pnts between plys.
[GeoLib] Documentation.
[GeoLib::PolygonWithSegmentMarker] Definition and impl.

Used in GMSH interface.
[FileIO::GMSH::GMSHPolygonTree] PolygonWithSegmentMarker instead of Polygon.
Style.
[FileIO] Impl. and use markSharedSegments().
WIP Tests for GeoLib::computeIntersectionPoints().