refactoring
- remove Services.java
- rename classes under actions.*
Adds the endpoint GET /resource/:pid/urn
- the response will be a URN object that contains status information
about the urn. The boolean field success signals if the resolver points
to the resource identified by :pid. Here is how an example object looks like
{

    "resolver": "http://nbn-resolving.org/",
    "urn": "urn:nbn:de:hbz:929:02-edoweb:17507685",
    "resolvesTo": "http://edoweb-rlp.de/resource/edoweb:1750768",
    "resolverStatus": 200,
    "success": false
}