Merge pull request #28 from playcanvas/master

merge
Merge pull request #29 from playcanvas/master

merge
[VERSION] v0.163.0-dev
no need for inverted X
no need for inverted X
no need for inverted X
New particle interface and underlying logic:
- reset() resets particle state, doesn't affect playing;
- stop() disables the emission of new particles;
- play() continues the emission, also unpauses;
- pause() freezes the emitter;
- isPlaying() tells if emission is in progress;
- "oneShot" parameter replaced with "loop" (same, but inversed);
- non-looped emitters do not start emission unless play() is called;

simple and sparks examples are updated.

Fixed CPU stretching.
Fixed WebGL warning spamming by disallowing particles being rendered into depth map. Added meshInstance.drawToDepth boolean to control it.
[FIX] Respect material face culling when rendering into shadow maps.
[FIX] Camera component now correctly sets the alpha value for the clear color.
Merge pull request #108 from guycalledfrank/particles-interface-stuff

Particles interface and stuff
[RELEASE] v0.162.2