Move extraction from a package to the model

Refactored extracting a file from a package to the model, and added a
dependency on atool so it can handle more file formats.  Also, escape the
relative paths coming from the URL.
Update LOCKSS-o-matic fields
Change LOCKSS download URL

refs #5425

Split chunks of an AIP are found at <aip_uuid>/download/<chunk_number>/
now, instead of the chunk number being passed as a GET parameter.