Support Analytics Service in ns_server

In a near-future release, we will be including the Analytics service as a sibling to query, indexing, fts, etc. This will require ns_server changes for managing the service, GUI changes for enabling it, etc.

Steve and others did a first pass at implementing this a few months ago, and I have been maintaining my own fork of ns_server with those changes at https://github.com/ceejatec/ns_server . I know that was put together fairly quickly so I don't know how well it might map to what we eventually want to have.

This is targeted for spock.next, but it would be tremendously helpful to Analytics if we could have something in ns_server much sooner than that. We are getting underway with true Couchbase Server integration and will need to have a proper ns_server codebase to work with. Might it be possible to have some conditionally-compiled code in master such that we can build with Analytics support while Spock builds continue without it?