Add support for full read/write access to cdrw media in packet mode

Currently ubuntu supports writing to cd media using track/session at once mode via growisofs. This allows adding files to a cdr or cdrw easily, but can not remove files to reclaim the space, or edit files in place. Use of packet mode allows the cdrw to be used like a giant floppy. This means you can mount it as a true filesystem so command line tools can see it, and you can delete files from the disc and reuse that space without having to reformat the entire disc.