Source Maintenance: fix various maintenance script issues

Source Maintenance: fix various maintenance script issues

* ensure auto-generated .list are sorted, instead of ad-hoc system
  dependent ordering which can cause needless updates.

* grep only paths with *.* (usually files) instead of all items in each
  directory. This avoids scanning sub-directory indexes with grep, which
  produces fatal errors on some systems.

* add check for Squid Software Foundation copyright blurb and highlight
  files needing attention.