Move off postgres / solidify storage traits so they don't depend on postgres semantics

[erikh]

The Record and RecordList traits are just fine, but other uses of the library -- especially inside the order handler itself -- causes trouble as well as one-off calls that would need to be re-implemented if trait implementations for these two were to be written.

So, here's a list of things that need to be done:

• Itemize and document concrete types that leverage the traits with postgres
• Itemize the methods that would need to be implemented by those concrete types if they were traits
• Write traits that mirror the new methods that need to be implemented
• Remove all direct database work from the order handlers specifically
• STRETCH GOAL: write a sqlite or redis implementation of all database code