MAINT-7926, MAINT-8400 - fixes related to bounding box and LOD calculations for rigged meshes in animated objects

MAINT-8608, MAINT-8539, MAINT-8615 - changes to make object animation info more persistent, tolerant to race conditions during initialization

SL-704 - first pass cleaning up comments. Also added LLControlAvatar::initInstance() as a potential hook for optimizations.

  -> Automatically whenever handle_reset_view() is called (i.e. Esc)
  -> Part of Advanved / Refresh Attachments
  -> Part of avatar context menu / Reset Skeleton

--HG--
branch : Appearance-Misc

MAINT-6645 - Improvement - Agents that render as jelly dolls should have their attachments render at 0 LoD to prevent loading higher LoD complexity in memory thus deterring crashes.
Stability improve.

SL-779 - refactoring related to rigged-mesh determination. animated objects must contain some triangles even if not at the root

Originally a fix for MAINT-4773. This was causing a number of issues since
changes made in this code were pushing null textures into server and viewer
should not modify 'content' at server of own violition.

MAINT-7870 - propagate new animated mesh flags even if they're being zeroed. handle notification of same to update control avatars on notification from elsewhere.

SL-808 - updated ARC display to largely work with animated objects. Gives some triangle information that we may or may not ultimately keep. Surface area calcs still not working

SL-794, SL-790 - viewer-side enforcement in UI for various animated object limits that are also enforced on the server.