Generic Stream support for OOP languages

Other issues related to Node streaming, read these for some context:
https://github.com/Azure/azure-webjobs-sdk-script/issues/1361
https://github.com/Azure/azure-webjobs-sdk-script/issues/660

We need to provide a generic stream abstraction in the RPC layer, which can provide stream inputs to various language workers (node, C#, Java, python, etc).

Need to investigate how streaming functionality may differ across languages - a concrete implementation for node may be the first priority, but we want to create that with other language in mind.

We need to consider how to handle streams as both a top level binding input (i.e. bind to the bytes in my blob), and a property in a property bag object (body property of an http message accessed as a stream).