cubicweb-celery #10363815 Configure celery from instance directory [validation pending]

It would simply be easier to drop a celeryconfig.py file in the app home directory, so that users can just read celery's doc.

prioritynormal
typeenhancement
done in0.1.0
load left0.000
closed by#163a41551c67 Move the configuration of celery into a `celeryconfig.py` file in the app home
patchMove the configuration of celery into a `celeryconfig.py` file in the app home [applied]