Improve lights

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24500 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Improve lights (position and shadow for close surfaces)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@24501 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e