[web] Only log exceptions in debug mode in Ajax controllers When we raise a RemoteCallFailed error (erroneously turned into a '500 Internal Server Error' response, but that's another business). In production environment, we do not want to log the exception in most cases where it's actually a client error. So only log the exception in debug mode.

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