When removing package also remove unnecessary dependencies.

Hi there,

   I been using smart package manager for a few years now and find it very useful so thanks for all hard work.

   However, when removing packages, only packages that depend on it are also sensibly removed. But lets say I install package X which depends on library Y. If I remove X, Y is not removed. I don't want Y any more and all it is doing is taking up space and nothing useful. And it will be very usefull and good if smart can do some "house keeping" and remove at least some dependencies like that, so I guess that would be checking one level of dependency tree. At least as a start.

   A more complex version can be developed later, which does more processing and perhaps lets user decide what other dependencies he/she wants to remove. I guess not always ALL dependencies are desirable to be removed.

   So a feature request would be to have a basic support for removing packages which are providers to a single package which previously have been removed.