Allow sending streams and not just receiving them

[ghostdogpr]

Messenger now has 4 different ways of sending a message:

• send for sending a single message and receiving a single response
• sendStream for sending a stream of messages without receiving any response
• sendAndReceiveStream for sending a single message and receiving a stream of responses (was previously named sendStream)
• sendStreamAndReceiveStream for sending a stream of messages and receiving a stream of responses