* Direct avatar rendering
This adds new template helpers for avatar rendering which output image
elements with direct links to avatars which makes them cacheable by the
browsers.
This should be a major performance improvment for pages with many avatars.
* fix avatars of other user's profile pages
* fix top border on user avatar name
* uncircle avatars
* remove old incomplete avatar selector
* use title attribute for name and add it back on blame
* minor refactor
* tweak comments
* fix url path join and adjust test to new result
* dedupe functions
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