Proposal: Interpreting Bindings

[tinygrasshopper]

What is the problem?
A description of what the problem is.

Currently the binding response from the service broker is not structured, brokers can returns anything in binding response, which is sometimes challenging for application developers to interpret.

Who does this affect?
Broker authors and application developers

Do you have any proposed solutions?
Lets introduce a concept of a "Kind" for a service, which can help us predict/interpret the binding response

Additional context
I have created a proposal here: https://docs.google.com/document/d/1VTDc_uAKOtIpYZCYMruGVHn2Gj7cKeyuTP9fmDwp46M/edit# please feel free to leave comments

Similar to
#116

[mattmcneeney]

@tinygrasshopper you should have a look at buildpacks/rfcs#22 when you have a chance - seems very related