Add Warning/Flag Support

[atla5]

• add responsive protections so that items which cannot be marked correctly are still catalogued in some degree (error parsing a contributor classification adds the names associated with it under the blank dc.contributor tag), flags the item, and presents a warning with an explanation of what occurred.
• Items which have some sort of error or reason for questioning their validity in a greater capacity (error parsing at all) should be tagged as problematic, potentially staged for review, and the user notified.