logilab-database #173520 Add missing password parameter for prompt-less backup/restore [in-progress]

cubicweb-ctl db-dump|db-restore show pg_dump|pg_restore password prompts even though the DB password is readily available in CubicWeb's all-in-one.conf.

The culprit is logilab-database which provides no way to pass the DB password when trying to back up or restore databases.

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patchAdd new {backup,restore}_commands_env methods [in-progress][postgres] Implement {backup,restore}_commands_env methods to remove annoying password prompts [reviewed]Add optional 'dbpasswd' parameter to {backup,restore}_commands methods [reviewed]