CRUD operations for Organizations

HYDRASIR-97
HYDRASIR-151 #close
HYDRASIR-152 #close
HYDRASIR-155 #close
Create a persisted organization model

HYDRASIR-97 #close
Add more organization_spec tests.  Tidy up error processing in organizations_controller.   Tidy up code in Organization class.

[skip ci]
Make use of CollectionModel.
Merge pull request #416 from projecthydra/feature/HYDRASIR-97-Organization

CRUD operations for Organizations