Renamed subject to resource as per the protocol

After discussing this with Lars Marius, we've decided that this better
matches the sdshare protocol which can only be a good thing.
Refactored the code to look up objects in ephorte

- Moved code out of EphorteHandler so this class mostly just deals with
  the parsing
- Gathered most of the code that interacts with Ephorte in the
  EphorteFacade
- Search for an existing object in Ephorte when the type of the setter
  argument is an ephorte object
Added test for creating referenced object