IntersectRegion[ <Plane>, <Polyhedron> ] : part 3 (save it correctly with output lengths)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23095 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Filename completing with .ggb in "Save as" dialog. (#2976)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23096 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Regular polygon doesn't show specific type string (triangle, etc.) since points length can change

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@23097 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e