N1QL Javascript functions : api/v1/functions endpoint should use a pre-defined port ETA:7/29

Currently the JS evaluator at api/v1/functions endpoint uses an arbitrary port. This mechanism has 2 problems:

1. It is not a user friendly way to dig the query logs to determine the port used by the JS evaluator
2. Security policies need a known range of TCP ports that will be used by couchbase. An arbitrary port does not help here.

I am marking this issue as a 6.5mustpass and beta as it might block users from trying out the new feature. If we are not fixing this for beta, we need to document it well.

7/26: The final outcome is the REST API outlined here:
https://github.com/couchbase/eventing/blob/unstable/docs/js-evaluator-rest.md