Version 0.2.1

This is mostly a bugfix release, fully backwards-compatible with v0.2:

• Fixed an occasional crash due to dangling callbacks in avatar fetching code
• Fixed unreliable network error handling leading to sync loop getting "unlooped" when server is temporarily unavailable
• Fixed a regression leading to bridge postfixes not being removed from user display names
• Fixed a regression manifesting in dysfunctional user name disambiguation
• Added User::rawName() to get a user name together with its bridge postfix
• Bridge names are now used as the first line of disambiguation, with user ids being the next (and ultimate) fallback.