Merge tag 'sparks-1.12' into develop

1.12
Re-work the PG stuff to set environment variables. This is known to be unsafe but all PG super-parameters are now handled the same way, which is simpler, and our servers are already only available on 127.0.0.1 and to developers only. We will make it stronger when we have the need.
Make the supervisor-related stuff completely project+environment aware, this allows deploying more than one project with all its environments on the same machine, which is needed on `obi`.
Make the PG env code a little cleaner, easier to read / find bugs.
Fix a variable name collision.
Revert ROLE to USER, there must be something missing.
Docstrings updates.
Temporarily deactivate the `install_components()` server-side contents until I clean the feature in my head and merge it somehow with the main sparks fabfile.
de-duplicate the `init_environment()`.
Install pip-tools too in dev target.
restart_gunicorn_supervisor(): use remote_configuration.tilde if env.user_home is not available.
Make the supervisor environment cleaner and allow the fabric `env` not to have it without crashing.
again. more. clean. do not forget. alternatives.
fix bug which made the Django settings not available if env.environment_var was not set. Indentation sucks sometimes. But I do not really mean it.
love to the local Django settings side…
Love to the local Django settings side, again; with a lazy getter, this time.
Love to the local Django settings side, again; we must chdir to the right place to import django settings…
DEBUG.
Django settings love… (again??)
Try to recover from supervisor corner-case situations without having the user to worry about it.