include the LinDA oracle

[rdanitz]

Revise the API docs of the LinDA oracle (formerly vocabulary repository) [1],
update as necessary and include the service into the backend (server.core.oracle).
Keep LOV [4] as is reasonable.
Come up with a robust solution to mock out the oracle API by a hard coded offline oracle for testing and debugging purposes – [2] or [3] should do.

[1] https://github.com/LinDA-tools/r2r-designer/blob/master/server/resource/public/api/vocab-repo.raml
[2] http://clojuredocs.org/clojure.core/with-redefs
[3] http://clojuredocs.org/clojure.core/with-bindings
[4] http://lov.okfn.org/dataset/lov/