Queryport API fine-tuning.

- made client.go API to generic.
- added SecondaryKey and IndexStatistics types in common/index.go
- export ResponseReader{} interface to consume queryport response.
  - protobuf.ResponseStream{} implements ResponseReader{} interface.
- updated scan_coordinator as per new API.
- updated n1ql integration as per new API.
- updated test-cases.
- updated scripts under tools/ directory.
- projector had to use adminport address obtained from ns_server.
  - remove adminport.listenAddr parameter from configuration.

Change-Id: I430f5c49507c8fd8f0ae6fc0b014e01ce14f4ab6
Reviewed-on: http://review.couchbase.org/43950
Reviewed-by: Sriram Melkote <siri@couchbase.com>
Tested-by: Sriram Melkote <siri@couchbase.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>