Improve skinning algorithm across rigs

[scottpetrovic]

I eventually need to improve the skinning algorithm for the weights.

• bending in the wrong spots (see human shins when feet are extended)
• "dumb" pass currently with applying 50% joint distribution around weights.

I will need to spend some time to see what is feasible that works across rigs.

[scottpetrovic]

I made a bit of improvements using some better targeted smoothing based on bone names. It is an improvement with certain things like the human lowerleg, but still has some issues on other areas like the wings. I will put out my improvements to main. I will leave this open as a general improvement task for the skinning algorithm.