Related T1835

Change double quoted comments to single quoted comments

To keep consistent comment format and to prevent syntax exception on jenkins build

Make changes as per review

Made changes as per review

use more imperative-like command names.
Aliases are used to keep old commands working.

Also add an explicit deprecation message in swh-scheduler's help message.

Related T1797

The migration is now done. No longer needs this adaptation code.

Related T1508

Related T1508

Prior to this, the select wanted to retrieve the new name to insert the old one
Ending up doing a noop.

Related T1508

Related T1508

in which (db|api)_testing.py files moved.

This is the contract that get_db/put_db is supposed to conform to.

extract:
- the 'task' group (and its related commands) in cli/task.py
- the 'task_type' group in cli/task_type.py
- remaining commands in cli/admin.py

the old "swh-scheduler" still exists for now, and is mostly backward
compatible but the --log-level option (which is defined in the "swh" main
command group).

Unit tests have been adapted and should pass ok.

Related T1508

Related T1629
Related T1508

This issue was spotted after the upgrade of psycopg2 to version 2.8

We kind-of-need that to test that we'll be able to understand results in
production (even though we're sending results by hand, not through this event)
and it works around https://github.com/celery/celery/issues/5366 in Celery 4.3.

This actually conflicts with the latest celery version.  We should not
depend on it as this is drawn by celery already.

this later does not brings anything over the default's one.

This requires swh.core >= 0.0.56

Celery voluntarily pools messages to reduce traffic, so it's expected that some
messages end up here several times. No need to spam logs about it.

The current state of the celery worker/utility logging setup makes us log twice:
the default value of log_console can't be overridden by the cli flag in celery
workers.

The environment variable can be set to journal when running as a systemd
service; this shuts down the console logger, and allows the metadata added to
log messages to pass through.

This also fixes the pretty-printing of tasks, which was ambiguous
(`42` and `"42"` where both printed as `42`).

This reverts commit 3939a41d.

Wasn't supposed to be committed yet.

Sphinx complains about it.

For uniformity with other SWH packages.