Updating value as blank using bulk import

Problem: How to remove a value from a field using update in bulk import? For example, a user might want to change the storage location to the virtual of multiple specimens in one go.


During bulk import, under the corresponding column in the CSV file keep the value as '##set_to_blank##'. This will remove the value stored in that field and update it to blank or no value. This is allowed only for optional fields. 

This will work for custom form fields too. If the value is just kept as blank, the system will ignore that column and not update anything for that value retaining the older value. This way, users can specify values only in those columns which need to be updated, and therefore it is required to set a value as '##set_to_blank##' correctly.