Add dynamic links and fix Filters compile error

[Ramblurr]

Fixes #4 and #5.

The dynamic links uses the @Url annotation from Retrofit. Links can bet fetched like so:

Service service = getSomeService();
String instancesLink = service.getInstancesLink();  // the server rendered link to the instances for the service
// fetch the instances for the service
Response<TypeCollection<Instance>> response = instanceService.getLinkInstances(instancesLink).execute();