Move environment specific info from code to config file

[EHJ-52n]

Currently, there is a hardcoded URL in the type HTTPPushListener:

    //TODO make configurable
    private static final String host =
            "http://ags.dev.52north.org:8080/enviroCar-broker/";

Please fix the given TODO in this line.

As shortcut, please remove the dev. part from the URL asap.

[autermann]

Still hardcoded, but the URI is fixed.