GFR: Rename records (file units and items) columns

[jmfcoleman]

We’re not sure users will understand what the records (file units/items) column means. It might be best to let researchers find these records within the context of the series description. Or, at a minimum, these columns should be renamed to make it more obvious to researchers who are not always familiar with NARA’s archival lingo and what these numbers mean. If retained, a hyperlink would be a great addition.