Add @defer support to the execution engine.

[michaelstaib]

https://www.apollographql.com/docs/react/features/defer-support.html

https://blog.apollographql.com/new-features-in-graphql-batch-defer-stream-live-and-subscribe-7585d0c28b07

https://www.reddit.com/r/graphql/comments/8wv1da/status_on_graphql_batch_stream_defer_live_etc/

facebook/relay#288

facebook/relay#2554

facebook/relay#2194

https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream

System.Net.Http.MultipartContent

[cgatian]

This would seriously blow people's minds.

[michaelstaib]

This is coming in April

[cgatian]

Dont tease me! April 1st? 😉

[michaelstaib]

We are aiming at April 14 or the week after that.

[michaelstaib]

#677