Remove index API

We have an index API that's only used by the functional tests, and is a passthrough to elasticsearch. I strongly believe we should remove it because it allows an admin to unwittingly (or wittingly) work around any access control and disrupt data. If manual intervention of an index is required, the admin might as well go straight to elasticsearch.

I DO think there's value in being able to prompt for a resource to be indexed, and possibly reuse the endpoint, but i think in the meantime we need to remove it before mitaka.

The functional test code in test_api will need altering to index directly into elasticsearch; it should be possible to alter this code to use the plugin code to write to elasticsearch.