return directly to interrupted actions+solution

I think in the action interrupted case, the best idea is to pass the interrupted action url through the signin process via cgi variables. (note, it could also be desirable to be able to preserve this action through signup and/or forgot password, but my inclination would not be to start there).

Perhaps we could even make all of this possible via AJAX, so that if I were to try to edit something in place for which I did not have permissions, I'd get sign-in options right there and then be able to continue in place.