fix for GitHub issue #31
more fix for GitHub issue #31
fix for GitHub issue #32
Improved finish features for more realism:

  - Radiosity support for brilliance is now available; to activate it, specify `brilliance on` in the global radiosity settings.
  - The brilliance effect can now be applied not only to incoming light, but also to outgoing light; to activate this, specify a second FLOAT value
    after the `brilliance` keyword. For maximum realism, both parameters should be set to the same value.
  - Fresnel angle-dependent attenuation can now also be enabled for highlights and the diffuse component, by specifying `fresnel on` directly in the finish block.
    (Note that you will still need to enable fresnel attenuation for reflections separately; also note that where reflection and highlights increase at shallow angles,
    the diffuse component decreases accordingly.) For a perfect match between reflection and highlights use the `albedo` keyword for the highlight with the same
    value as the reflection maximum; the reflection minimum should be set to zero.
Merge branch 'master' into feature/colour_model
More work on a well-defined colour model.