Optmisations and Experimental Toon Hatching Shader

This release should improve the performance of the shader and includes some minor improvements.

It also includes a new (experimental) toon hatching shader. It is available as a separate material and uses a single texture with a hatching pattern to create a (cross) hatching effect. The hatching shader is also compatible with attenuation and multiple light sources.

Fix for using the shader in a ShaderMaterial

Fix:

• Add a default value for the steepness parameter so ShaderMaterials using the shader do not break