Introduce non-CRUD operations

[bcogrel]

Third step discussed in http://lists.w3.org/Archives/Public/public-hydra/2014Jun/0082.html . Started from a suggestion of Markus Lanthaler.

Resource objects would have additional methods for non-CRUD hydra:Operations .

The parameters of these methods would correspond to RDF properties of the representation sent to the Web API. Of course, such representation could be translated before being sent to the Web API.

For more details, please refer to the mentioned thread.