SL-271 WIP - skip rendering bones with no end (set as 0 length). Show bones if show joints is enabled in mesh upload preview.

SL-271 WIP, SL-201 WIP - leaf joint attrib is now end. Show bones option now includes occluded portions.

SL-271 WIP, SL-201 WIP - add support for end point to joints, use for debug rendering display to show bones.

SL-201 WIP - avatar_skeleton.xml tweaks for aliases, removed wings and tail from default definition.

SL-263 FIX - fallback code to prevent crash, won't be invoked unless there's a bug somewhere upstream.

SL-266 WIP - removed obsolete rigParityWithScene code, set legacy and joint offset upload based on AND-ing state of all meshes in file.

SL-114 WIP - constrain uploaded meshes based on max joints per mesh. Set max joints per mesh to 110. Also fixed some uninitialized members of LLModelLoader.

SL-234 WIP - moved LLSkinningUtil funcs to separate class/files. Remap weights where needed. Warn that related debug settings require restart to take effect.