add stub of default script
Merge pull request #2479 from ZappoMan/defaultscript

add stub of default script
sanitiy checking when unpacking AvatarData update
use glm::isnan() everywhere for portable code
Merge pull request #2477 from ey6es/master

Adjust avatar LOD more aggressively: raise detail slowly when above our ...
Merge pull request #2484 from AndrewMeadows/sanity-checking

Sanity check AvatarData packets as they are unpacked