* enable willSendResponse to return a modified response
* add formatError as an extension that wraps engine reporting
* ensure that formatError once on every error path
* move old formatError express tests into integration suite
* add error lifecycle with minimal engine reporting check
* increase granularity of formatError test
* return 400 error for GraphQL error created by context
* add check for internal server error for errors thrown in context
* comment about context error status code
