eliminated rsurface.model, so there is now no dependence on having an

eliminated rsurface.model, so there is now no dependence on having an
actual model in the material renderer
(except transparent surface queuing still needing an entity)
this cleanup means that the material renderer could be called from other
places without an entity (effects such as particles and lightning beams)

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@7359 d7cf8633-e32d-0410-b094-e92efae38249