Set appearance refresh to false by default.

This setting was originally added some time ago to deal with issues where appearance was not received properly by all users.
However, it does not scale well with large numbers of agents.
Disabling to see if the original problem has abated or whether this will have to be tackled in another way.
Do not add attachments to the region scene object backup list.

Attachment persistence is not handled in this way and this just results in a load of busy work until a check in each SOG terminates a backup check for attachments anyway.
Don't unnecessarily remove from backup objects that were not directly attached from the scene.

These are never in region backup in the first place since recent 11830c43
Extend regression test to check backup status.
Add "debug lludp throttle log <level> <avatar-first-name> <avatar-last-name>" to control extra throttle related debug logging.
Add "debug lludp throttle status" command to return status information about a client's throttle (currently just whether adaptive is enabled).