WebStyle: better IP check in proxy configurations
WebStyle: better IP check in proxy configurations

* If the system is using a multinode setup, but the proxy IP
  is not part of the CFG_WEBSTYLE_REVERSE_PROXY_IPS,
  alert the admin and return a different default client IP address.

tiborsimko/invenio,tiborsimko/invenio,inveniosoftware/invenio,inveniosoftware/invenio