Turn on/off events by participants.

Up to now events could be turned on and off by resources. To turn on
events you still have to do it by resource but have additionally
the possibility to control it by participant. Only if both switches are
on, the participant will get events generated through the resource.
New resource /sys/configs

Every participant could GET and POST to this resource.
A GET might show this:

curl ... -H 'Content-Type: application/json' \
  -X GET https://ecs.host.com/sys/configs

{
  "participant_events": "true",
  "resource_events": {
    "/campusconnect/glossaries": true,
    "/campusconnect/course_urls": true,
    "/campusconnect/course_members": true,
    "/campusconnect/wikis": true,
    "/campusconnect/directory_trees": true,
    "/campusconnect/learningmodules": true,
    "/campusconnect/groups": true,
    "/campusconnect/categories": true,
    "/campusconnect/courselinks": true,
    "/campusconnect/organisation_units": true,
    "/campusconnect/files": true,
    "/campusconnect/terms": true,
    "/campusconnect/courses": true,
    "/sys/auths": false
  },
  "selfrouting": "false"
}

Only if participant_events and the appropriate resource_events are true,
you will get an event.

It's also possible to set the two attributes participant_events and
selfrouting. Just make a POST such as:

curl ... -H 'Content-Type: application/json' -X -X POST \
  -d '{"participant_events":true}' https://ecs.host.com/sys/configs
or
curl ... -H 'Content-Type: application/json' -X -X POST \
  -d '{"selfrouting":false}' https://ecs.host.com/sys/configs
or
curl ... -H 'Content-Type: application/json' -X -X POST \
  -d '{"selfrouting":false, "participant_events":true}' \
  https://ecs.host.com/sys/configs

As you see, just set the attribute you want to set and make a POST.
You don't have to provide a receiver header, because the receiver is
implicitely the ECS.
nginx has trouble with some links

Changed *_url routes to *_path routes.
Fixes #2