Make pycdio and cdio optional.
Add debug. * morituri/rip/drive.py: Show all drives, not just the ones that happen to have an Audio CD inserted.
* morituri/rip/main.py: * morituri/rip/drive.py (added): Add 'rip drive list' command to list available drives. * morituri/common/accurip.py: Add force. * morituri/rip/cd.py: Add --output-directory argument.