tableverse/avatar: Initial rewrite in terms of KineticThingyDelegate.
tableverse/avatar: Draw label using current ui colors.
tableverse/avatar: Fade in labels when mouse enters an avatar.
allverse/user, app: App rather than user now responsible for syncing "my" ui_colors.  Fixes several bugs.

Previously, the user thingy attempted to monitor and set the ui colors.  But this had issues because there are many users, but only one current user.  Instead, app now connects the user thingy to the current ui colors.