Order packages in packages.config the same was as CoreXT

[jeffkl]

If a user copy/pastes a list of packages from a corext.config, the properties are not generated the same. CoreXT sorts the packages so that the highest version of the package wins. We were respecting the order inside the packages.config but we don't really support multiple versions so the last declared package would win. This now sorts the packages so that the last one is the highest version which mirrors the functionality in CoreXT