Bug 9121

Currently, when you remove a package from a custom image, we tell you about the reverse dependencies of the package you are about to remove, but we don't remove the reverse dependencies (see attached reverse-deps-dialog.png). 

This creates a very cumbersome removal workflow, since you effectively must remember the list of reverse dependencies and remove them one by one. 

The dialog should instead remove the selected package and its reverse dependencies when you click the 'remove packages' button. It should look like the attached new-reverse-deps-dialog.png

Note that: 

* The dialog shows the number of reverse dependencies. This is not a random thing. This number is a very good high level indicator of the impact that removing the package will have, particularly since the number of reverse dependencies can be quite high and you might not be able to see the entire package list without scrolling.

* The list of reverse dependencies should include package groups, since the package group break down mechanism we have in place for removals means that Toaster is likely to do the right thing (remove the package group itself, and the package you selected for removal).