* Contact: auto-follow-back
* Shareable: create share visibilities

all visibilities are already in the conversation, so we can send
all notifications at once.

* conversations
* messages
* photos
* polls
* poll answers
* poll participations

fixes #4697

first implementation of receive_entity callback

and do some refactorings

move it to Diaspora::Federation::Entities and use it in some tests, but most of the tests can be removed later.

Change 'Sign up' to 'Create account'

Bump eslintrb

[ci skip]

Redesign default.haml

closes #6878

This reverts commit 18110288.

Add rel="noopener noreferrer" to autolinks