switch from using flat statuses to using error lists (decent chunk of work)

[jmartin-sul]

Turn the flat status that objects currently have into a list of error codes. A single status seemed like a good idea at the start, but as we got into tricky precedence issues when multiple statuses might apply, we realized that an error code list would have likely been the better choice. However, we didn't feel we had the time to rework this, and the impact on existing tests would be significant.