[server] Warn instead of failing when a looping task is registered and repo has no scheduler We should provide a way for client code to detect if they should register the looping task or not. See next patch for that.

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances