Establish a protocol for streaming

[DavidGregory084]

The streaming handler code in scaffold has no protocol as such.

The existing code is basically a toy that only works if you hardcode the number of messages you send and the number of messages you expect to receive.

Need to choose a JSON representation for stream element messages and for end of stream.

Also, timeouts to stop clients from blocking handlers forever waiting for end of stream if the client fails to send it.

[DavidGregory084]

This is irrelevant now as that code has been removed