do tox install with pip -e

PR #2413 added an issue template, but just adding files to the project
directory upsets the packaging scripts: we need to explicitly include or
exclude them.

Move the template into a .github directory to make that easy, and to de-clutter
the root a bit.

- this ensures we end up with a working virtualenv which we can use for other
things.

Document known to work postgres version

.. because I want to make the 'install_and_run' script useful for non-synapse
jobs, which do not accept --python. In any case we set up the path here, so
sytest shouldn't be guessing it.

.. because I want to make the 'install_and_run' script useful for non-synapse
jobs, which do not accept --python. In any case we set up the path here, so
sytest shouldn't be guessing it.

Tweaks to the upgrade instructions

Improvements to the federation test client

python_dependencies: Use bcrypt module instead of py-bcrypt

so that you don't necessarily need a config file.

Add prometheus config

Issue template for Synapse

Make it read the config file, primarily.

Added instructions for checking server version.

Responding to review comments.

... from https://github.com/matrix-org/synapse-prometheus-config.

Add missing parameter to _base.start_worker_reactor

escape the % that got added in 92168cbb so that the process starts up ok.

Allow configuration of CPU affinity

Make it possible to set the CPU affinity in the config file, so that we don't
need to remember to do it manually every time.

We have 10 copies of this code, and I don't really want to update each one
separately.

Removed the sentence encouraging people not to file a bug - if people are in doubt we'd rather they filed a bug than gave up entirely.

Oops capital L.

A new issue template proposed to try and steer people towards #matrix:matrix.org for support queries relating to running their own homeserver.