* Added support for returning status codes from checkRequestIsValid / checkStorageRetrievalRequestIsValid / checkILLRequestIsValid instead of just a boolean, with the old boolean style still supported.
- Made Demo driver always return the new-style array and occasionally return different messages for request validation failures.
- Removed the now-unused blocked* actions.

- Group holdings by holdings ID and location by default to accommodate a situation where the items under a single holding have multiple actual locations. This will not change anything in the more common case where there is a 1:1 correspondence between these values.

- Handle purchase history separately from text fields since it's different. 

- Fixed Voyager "no items" status and holding grouping to always use MFHD_ID as the group key with a prefix to make sure the MFHD_ID is never mixed with a proper ITEM_ID.
- Also added missing RETURNDATE field placeholder in getHoldingNoItemsSQL()