Particle system big update

 Velocities are now primary way to specify particle motions. Offsets are removed. Simulation works differently. Internal data layout changed.

Divergence now specified as 2 curves with random point between them. So the formula is lerp(param, param2, random).
rate and lifetime can be randomized;
added startAngle parameter;
faster stretching;
speedDivs are removed;
fixed NPOT particle count bugs;
fixed particle spawn positions to match respawn positions (original spawn pos ignored emitter rotation);
dynamic change of oneShot behaves differently (not fully correct but less buggy);
particle random seed now changes after each new emission;

This version doesn't work on iPhone or something else low on uniforms. I'll commit a fix ASAP.