Names "PolyhedronNet" >> "Net"

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@31317 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Icon for net tool

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@31318 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
instanceof GeoPolyhedron >> .isGeoPolyhedron()

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@31319 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e