medication-prescribe hook should support multiple medication prescriptions as context

[kpshek]

Ken Kawamoto pointed out that in our documentation for the medication-prescribe hook we state that the context is "The set of proposed medication prescriptions".

This makes sense that we would support multiple medication prescriptions as context. However, in our example and in prototype implementations, I know we've only ever sent a single medication prescription as the context.

We need to think through this. I think that it does make sense for the context in this case to contain multiple medication prescriptions.