Aqsis skin shader improvements

Yesterday I've committed some important improvements of skin shader for Aqsis.
Because the accuracy of new mesh topology, we can use an internal baking engine, based on vert shader. It require just few seconds to be generated, and the results are enough good to be used as scattering light map(see image below).

Another good notice is the new rendering pipeline finally remove (or better, make almost invisible) the "famous" seams artefacts. Further improvements are possible (precalculated AO, better scattering by channels, separated eye geometry and materials) but the level is already satisfying. The image below is just a quick test with "Caravaggio's lights", rendered with Aqsis 1.6: