WebSubmit: new websubmitadmin CLI

* Adds websubmitadmin CLI to dump and diff submissions.
  Heavily inspired from CERN submission dumper tool from
  Tony Osborne.  (closes #1334)

Co-authored-by: Tony Osborne <tony.osborne@cern.ch>
Tested-by: Tibor Simko <tibor.simko@cern.ch>