Support for input and output bindings

[zroubalik]

We should discuss whether it is worth to explore possibilities on enabling Binding concepts for a function, see Azure Fn.
If we decide to try it, we should try to follow Azure Fn's syntax for the Bindings definition.
It would require a framework/library for enabling the bindings for users in a function.

[lance]

@zroubalik I think we should adhere as closely to the Azure Fn syntax as possible (ideally there should be some level of portability).

Here is a complete list of Azure's supported bindings: https://docs.microsoft.com/en-us/azure/azure-functions/functions-triggers-bindings#supported-bindings

This is the context object's API, which we should also consider adhering more closely to. https://docs.microsoft.com/en-us/azure/azure-functions/functions-reference-node#context-object