Ability to query step status as JSON document

The application should provide an API to obtain information about a given process or project. External application should get information by requesting a service URL (e.g. http://my.goobi.org/process/<ID>) and get a JSON response describing the process and it's current state of work. The API should only accept content type text/json for now. Different content types are generally possible in the future and should be available via content negotiation.