Code for user groups roughed out

There's now a FileRegex class, as well as a ArkUsers rolon. There's even a method on Env to check to see if the user is in a particular group for the given cabinet.

Lots o' new code, none tested. :-( But its gotten late again. Time for bed.

My plan is to add checks to the restrict command. I've still got to figure out what's next. Perhaps working on the portal, so that scripts are atomic--nested transactions still need to be tested!

Bill