Graylog2 path fixes

On the off chance that any else is trying to run Graylog2’s web interface at a path other than the root of a URL (e.g. instead of, I have a repository at sciurus/graylog2-web-interface that fixes places where absolute URLs crept in to the code. The Graylog2 developers are rewriting the web interface in Java, so I’m not sure if there will be a release in the 0.12 series with these changes.