Remove federation related docs to split using and operating a bhub docs

[choldgraf]

This is a general docs improvement that does a bit of restructuring and tidying. It also complements jupyterhub/mybinder.org-user-guide#213 as I moved over some content to these docs from there.

cc @consideRatio in case he wants to take a look at these too ;-)

[choldgraf]

thanks - both applied! I also turned on readthedocs preview builds and if that works, will remove the circleci build (since it's just for docs preview)

[consideRatio]

Other than the requirements.txt details that I wish no-one need to experience debugging more than me and I think @sgibson91 have already ended up doing, this LGTM! Thank you for your excellent work to make the documentation so great @choldgraf !

[betatim]

WDYT of the new title? I couldn't resist trying to find an alternative to the very generic one

The federation related things that have been removed, did they get added back somewhere else in a different repo/page?
edit: somehow the link to jupyterhub/mybinder.org-user-guide#213 got parsed as a link to some issue when I read the description, in fact it is another PR

[choldgraf]

I just added back in Sphinx - I think at a location that does not trigger the bug @consideRatio mentioned? Is that right @consideRatio ?

Anything else to take care of here?

[consideRatio]

@betatim this LGTM, merge agreement?

[sgibson91]

LGTM! 🎉