MB-12750 partially forwarding /internalSettings requsts to goxdcr
MB-12750 partially forwarding /internalSettings requsts to goxdcr

- GET retrieve values from goxdcr and merge them with ns_server internal settings
- POST process all settings known to ns_server and forward the rest of them to
  goxdcr

Change-Id: I0f21214f035323795b166f64868e06e5ad26e0d7
Reviewed-on: http://review.couchbase.org/44258
Tested-by: Artem Stemkovski <15a0730a27c69f62ab86f2b6c639fca202166c02@couchbase.com>
Reviewed-by: Aliaksey Kandratsenka <340b8e09ca65cd3fc686427fcfed17e87eaf61e2@gmail.com>

nimishzynga/ns_server,ceejatec/ns_server,mschoch/ns_server,membase/ns_server,membase/ns_server,membase/ns_server,nimishzynga/ns_server,ceejatec/ns_server,nimishzynga/ns_server,ceejatec/ns_server,membase/ns_server,nimishzynga/ns_server,mschoch/ns_server,mschoch/ns_server,ceejatec/ns_server,membase/ns_server,mschoch/ns_server,nimishzynga/ns_server,nimishzynga/ns_server,mschoch/ns_server,membase/ns_server,mschoch/ns_server,ceejatec/ns_server,ceejatec/ns_server