Auto Shadow Bias calculation. Fix for bad NaN normals. Fix in Clay Render, now forcing diffuse reflection to 1.0

Forcing diffuse reflection to 1.0 in Clay Render, as it was incorrectly keeping the original material diffuse reflection in the previous beta.

The rest of the fixes and improvements have been made to Core:

Automatic calculation of Shadow Bias and Minimum Ray Dist depending on the scene size, to avoid black artifacts in big objects.

This is a very experimental feature that may introduce some artifacts to the images. We need to test thoroughly but seems to be working ok for now and fixing most of the black artifacts. I have seen some new minor white artifacts in some cases but they seem to go away with AA.

Also, fix for bad NaN normals that can happen sometimes.

New Clay Material, Oren Nayar sigma texture, neg color Musgrave fix

v0.1.99-beta1

Version, DLL and Readme changes. Integration of new Clay Render and O…