CURL : Create custom http header for N1QL CURL to allow localhost endpoints to enable/disable access

Add a custom header to all requests sent by N1QL curl :

For example : X-N1QL-CustomHeader : This request is sent from N1QL CURL.

(Use standard for custom headers : [*http://stackoverflow.com/questions/3561381/custom-http-headers-naming-conventions*])

Have all the localhost endpoints check when being accessed and manually reject any requests with the above header. For all external endpoints the header is ignored. This will create a dependency on our localhost endpoints to check for this header and actively reject access to N1QL CURL.