Moved new extrude example into "webgl_geometry_extrude_uvs.html". This example still needs some work ...

Also added ArrowHelper to "webgl_geometries.html"

Added workaround for ANGLE bug which was breaking shading when using physically based specular term.

See discussion here: https://github.com/mrdoob/three.js/pull/1518

Issue 1: when having multiple ParticleSystems, starting since second one particles got sorted according to wrong matrix (it was cumulating all transforms).
Issue 2: particle sorting was using camera transform from the previous frame.

This commit is scary, lot of potential for something getting messed up in a subtle way.

This fixes issue #1504

Something similar would have to be done in Projector.

Also while at it I found particles sorting is incorrect: it uses camera info from the previous frame plus _projScreenMatrix gets multiplied more times when there are more particle systems.

This is required for SSAO. Unfortunately scene.overrideMaterial is not enough for proper depth pass. Like for shadow maps, shader animated objects (like morphs) need different depth materials than static objects.

 - Some routines are moved to independent functions.
 - Removed unused variables.
 - Features are not changed.

These were coming from the initial setting of weapon, when there was no active animation yet (as behavior didn't get yet to select the animation state).