RootInstaller: warn me about new permissions when upgrading/installing

If an app requires new permissions with a new version, there should be a (at least optional) popup. I can see the list of permissions in the app screen, but I'd have to compare it manually to the previous one to even notice a change in permissions.

I think this is useful if the app does exactly what I want and there is no reason to give it more permissions for dubious features.

Also at the moment it is not possible to see the permissions of older versions if they differ from newer.