Adds NPREffect to library

[walbourn]

NPREffect added which implements Cel (Toon) shading and Gooch shading.

• With and without a base texture
• Supports a specular threshold (rather than a Phong specular dot) with a smoothing factor
• Supports rim lighting: outline for toon, additive for gooch
• Supports instancing

NPREffect also supports MatCap shading.

• With and without a base texture
• Supports instancing

[walbourn]

Test coverage walbourn/directxtktest#73

[azure-pipelines]

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