This reverts merge request !733

Extract the login responsible for obtaining websocket URL into the corresponding
Endpoint function.

splits actual nodeinfo generation into raw_nodeinfo, the 2.0 handler
gives the same result, while the 2.1 handler inserts the
software.repository field. requested by @href

that is the only change from nodeinfo 2.0 to 2.1

also this makes the nodeinfo tests use 2.1.json instead of 2.0.json

Setting it to true will actually override a 'false' set before.

This reverts merge request !682

* federation (ap, salmon)
* media (rich media, media proxy)
* upload (uploader proxy)

Each "part" will stop fighting others ones -- a huge federation outbound
could before make the media proxy fail to checkout a connection in time.

splitted media and uploaded media for the good reason than an upload
pool will have all connections to the same host (the uploader upstream).
it also has a longer default retention period for connections.

activitypub: utils: update the state of *any* pending follow relationship that matches the actor and target

[#534] Made federation push sender be determined basing on content instead of `referer` header. Updated tests.

This is in preparation for 1.0. We'll be able to switch the config to the new
mechanism on PleromaFE then as well.