- Return all images as og:image
- Return videos as og:image (preview) and og:video
- Return profile:username on profiles

* add og:url to stream_item view

* add og:url and text to about/show

* add og:url to profile, followers and follows pages

* Add meta tags for OGP to following & follow page

* simplify render helper

* Follow up #2133

* og:type is only accounts/show

* revert accounts/{following,followers}