moved all type-specific model fields to respective structures (alias, sprite, brush)

moved all type-specific model fields to respective structures (alias, sprite, brush)
renamed model_t brush to brushq1, and created brush, brushq2, brushq3, currently brush only has entities, all else is type specific
wrote the beginnings of a q3 bsp loader (and of course the headers)
added functions CL_PointContents and CL_FindNonSolidLocation to simplify queries of world model (and make it more maintainable when q3bsp support is finished)
added r_shadow_glossintensity cvar (default 1) for glossmap textures
added r_shadow_gloss2intensity cvar (default 0.25) for forced gloss

git-svn-id: svn://svn.icculus.org/twilight/trunk/darkplaces@3284 d7cf8633-e32d-0410-b094-e92efae38249