Background color for 3D view

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@31260 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
polygon triangulation (step 9 : set of simple polygons : fix first/last)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@31261 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
#3947 IFrame load problem fix

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@31262 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e