Pre-validate designs before starting to write anything

[jkuester]

Currently we check that amount and getDoc exist in a design before writing any docs for that design. If the design is missing one of these values, it is skipped, but the rest of the designs from the file are still processed and the docs written. It seems like it might be better to not write anything if we detect that the design is bad.

We could pre-validate the whole design array before starting to write any of the docs. That way, we should never skip any docs once we start writing....