0.0.6.9 released, please help hunt the nasty bug down..

I've released 0.0.6.9 . This isn't 0.0.7 because it has an annoying and intractable bug, documented in the release notes and the README. Basically, updating the package lists and installing packages will sometimes crash the program. If you are familiar with C++ programming, it would be great if you could try to find this, especially as I'm short on time at the moment.

This release also adds multilevel undo support and support for actions on package groups.

Daniel