Give focus to DialogBoxen

In particular, the open, save and run dialogs.
Add "Enter" and "Esc" shortcuts to model open dialog

Hitting “Enter” key fires event for “OK” button on dialog. Hitting
“Esc” key fires event for “Cancel” button.
Add "Enter" and "Esc" shortcuts to model delete dialog
Add ModalKeyHandler to encapsulate "Esc" and "Enter" key presses
Use ModalKeyHandler in open and delete dialogs
Use ModalKeyHandler in model save and run dialogs
Use ModelKeyHandler in logout dialog