InternetArchive/repair_assets: Accidentally reverset the "sanity check"
logic, so put it back the right way!
InternetArchive/view_derivatives: Started on the POD documentation but
didn't get very far.
InternetArchive/view_derivatives: New Perl script which Reads JSON
metadata from the IA and builds tree-like structures linking
original and derived files on the IA. It reports these trees and
saves a subset of derived files in an output file to be used for
deletion. In general we do not want derivatives, we make them
ourselves. Older software had no reliable way to prevent them.