I understand that this change is quite unreadable and hard to review, sorry for forgetting to do atomic commits. This patch does not change too much content wise, it just
* Gets everything from gitlab wiki
* Removes some specific gitlab hacks
* Formats all documentation file names to be in snake case so they look the same way as our code does

This is to make it easier for the frontends to handle domain.com/users/nickname
urls.

Add a section on how to identify a pleroma instance, clarify that post upload limit is not capped too

Remove a limit on attachments in Mastodon API and document the changes in responses from vanilla mastodon