Handle accentued characters in nuxeo.conf

If a property in nuxeo.conf used an accentued character, it is wrongly encoded in the target XML file.

For example, add the following line in nuxeo.conf

nuxeo.notification.eMailSubjectPrefix=Nuxéo

It will produce this line in nxserver/config/notification-config.xml after running the command nuxeoctl configure

      <eMailSubjectPrefix>Nuxéo </eMailSubjectPrefix>

The expected result is

      <eMailSubjectPrefix>Nuxéo</eMailSubjectPrefix>