Support importing/exporting package group filters
Support importing/exporting of package group filters. It looks like currently, we just export the name of the package group that the filter rule is acting on but this is insufficient since the name could exist in two different repositories. You'll note for example that you can see package group AND repo name when you go to create a package filter rule.
Also, we need to support importing of package filters. It looks like the code that exists is incomplete.