Changed include to shellImport, and added convenience command import to command shell
Added defined() method to Groovy scripts to check if a variable is defined
GUI updates:
- improved handling of shutdown()
- customizable GUI title
- gui variable exposed in shell to allow scripts to interact with GUI
- improved caret positioning during history navigation
Nicer tabular message details pane
Better handling of shutdown for shells
Added closures to allow GUI to be updated from shell scripts
Changes to shell GUI placement strategy to avoid overlapping multiple shells