AvatarService -- add two new methods, GetAppearance and SetAppearance
to get around the lossy encoding in AvatarData. Preseve the old
functions to avoid changing the behavior for ROBUST services.
AvatarAppearance -- major refactor, moved the various encoding
methods used by AgentCircuitData, ClientAgentUpdate and
ScenePresence into one location. Changed initialization.
AvatarAttachments -- added a class specifically to handle
attachments in preparation for additional functionality
that will be needed for viewer 2.
AvatarFactory -- removed a number of unused or methods duplicated
in other locations. Moved in all appearance event handling from
ScenePresence. Required a change to IClientAPI that propogated
throughout all the IClientAPI implementations.
