shaders : lights

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@30507 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Intersect through sphere 80% opaque

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@30508 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Fix for #3763

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@30509 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e