Fixed bug where depth buffer is not cleared if last object rendered on previous render cycle disabled depth mask.

I think dev branch should have docs corresponding to dev branch code.

Shadows should be now done more correctly and also be a bit less fussy. Before RGBA encoded depth maps were getting messed up with blending (that's why everything was extremely sensitive to frustum size).

All examples with shadows had to be re-tweaked (shadows now behave differently).

Plus added "onUpdate" callback handling also for cube textures.

This is necessary for OpenGL where pow(0,0) is undefined and apparently can be negative, leading to negative specular light (in DirectX you just get zero).

Also some more refactoring in IcosahedronGeometry and tweaks to geometries example.

Made by hand, trying to give more shininess to nose, forehead and lips, less to everything else.

Also refactored a bit regular Phong shader and refreshed Lee-Perry normal map example to be less zombie-like.

Except special cases like 3d renderers and cube cameras all examples should be now without warnings.