msfconsole 'edit' command

Useful for quick editing a module during development / bug fixing.

I don't really see a security issue with running a command defined in the user's VISUAL or EDITOR environment variables;  if the user can run msfconsole to begin with, there are better ways to get into trouble.

Anyway, it's kinda fun. I'm moving on to Rubymine, slowly but surely, so maybe I'll never use this, but I imagine plenty of people still use an $EDITOR to do little things like fix spelling and whatever.