Sprite functionality via materials/surface flags

[trak]

It would be nice to be able to get textures to behave like sprites using either the material definition or a surface flag. This could be useful for sfx like flares or background/small details.

An additional feature that would be nice to have a special sprite function that restricts the sprite's rotation to its longest axis, similar to what 'deformvertexes autosprite2' does in q3 . This is especially useful for things like long animated energy beams.

Q3map2 shader manual entry for autosprite2: http://q3map2.everyonelookbusy.net/shader_manual/ch2.htm#deformvertexes

[jdolan]

Vertex deforms have been a // TODO: for quite a while. I'll try to get these done for the beta.