Major:
 - If possible open sg subsystem Read-only to work around NOMEDIUM error with encrypted partition
 - Handle ctrl-c
 - Documentation
 - Further documentation of U3 features
 - Document which options are destructive
 - Don't allow enable security if security already enabled
 - Don't allow disable security if device locked/not secured.
 - [SG] retry on busy error
 - MacOS X support

minor:
 - ETA when loading new CD image
 - Disable Cursor on progress bar
 - Display info if no options provided
