comet like object, fake volumetrics tweak

as the title says, tweaking the fake volumetrics from the fireball tutorial into a comet-like object. final comet should have this particle-dust, and some dupliverts for ice-crystals

need to animate the textures still.

I achieved the unregular movement by a vortextfield

complete 110 frames in 10 minutes, if it stays this way its perfect.

yet its still not usable for still-renders or far distance viewing, the textures look too uniform