Advertise to others whether we have chat circling enabled, only include people
with it enabled when doing the computations.
Only render ball avatars when "avatars as balls" is checked.
Re-request skeleton/face URLs on login.
Initialize chat circling flag.
Merge pull request #1294 from ey6es/master

Tweaks for Grayson's camera request: chat circling toggle goes both ways, allow invisible avatars by clearing URLs.  Also fixed switching models on login.