If the "use_site_small_logo_as_system_avatar" setting is enabled, the site's small logo is displayed as the selected option by the avatar-selector. Choosing a different avatar disables the setting.
* DEV: Remove unused omit_stats variable from user serializer
This was hard-coded to true in a8b5192efd43bcbf64ffe7ae44e5c5b7f3be0b51, and is no longer used anywhere
* Remove attribute declarations
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
