Merge pull request #19 from playcanvas/master

merge
Fixed appearance of different blends, removed premultiplied blend from particles;
Fixed lifetime change weirdness, removed lifetime2;
Fixed alpha2 not working in CPU mode;
Fixed preWarm;
Fixed bug with color intensity multiplying alpha;
Particle gamma correction is now off when no lighting is enabled on particles;
Fixed possible error on dynamic 'lighting' parameter change;
Fixed system disappearing after changing oneShot a few times;
Fixed endTime calculation for oneShot emitters (didn't take rate2 into account).
Merge pull request #77 from guycalledfrank/particle-system-fixes-new

Particle system fixes (new)