Allow querying during `clinvoice create` operations

[Iron-E]

Right now, one can only be presented with an input::select / input::select_one prompt with every single entity in the system (of the proper type) when being asked to create a new entity which references another (e.g., Organization references Location). Instead, we should allow users to query this information if they choose.

Take care to remove duplicate logic between clinvoice create and clinvoice retrieve while doing so.