Make the dependencies more like a standard Python project and hook up the optional dependencies to setuptools (#4298)

This is based on the work done by @krombel in #2601.

https://github.com/vector-im/vector-web/issues/1977 --> https://github.com/vector-im/riot-web/issues/1977
And mention of Vector as a client replaced with Riot.

Signed-off-by: Ashe Connor <ashe@kivikakk.ee>

Signed-off-by: Slavi Pantaleev <slavi@devture.com>

Signed-off-by: Aaron Raimist <aaron@raim.ist>

... to stop things which try to import `types` getting `synapse.types` instead

Link to contrib/docker

wrap at 80ish

This addresses #3224

Especially useful for the debian repo, as this makes it easier to get the key in a secure way

It has been over a year since any code has been commited. Some of the relevant links in
the documentation are broken, but since no pull requests are being accepted, they
won't get fixed. We should probably remove this from the README.

Signed-off-by: Silke Hofstra <silke@slxh.eu>

update docker hub url

Signed-off-by: Jeremy Cline <jeremy@jcline.org>

Signed-off-by: Andrew Conrad <aconrad103@gmail.com>

* document how to make IPv6 work

* spell out that pip will install 17.1 by default

The FreeBSD port has been moved to the net-im category