Remove http support for neptune queries in favour of using the SDK

[andreachild]

To decrease complexity and improve maintainability of the project it would be good to remove http support for neptune queries in favour of always using the aws javascript SDK. Removing neptune queries over http would remove the need for the http lambda template and improve user experience by reducing the number of command line options. One caveat to http removal is that old versions of neptune which do not have SDK support will not be able to use the graph QL utility.