HaikuDepot: Store BPackageVersion in PackageInfo...

...instead of the string representation. This makes it easier to
get the major, minor, micro, prerelease and revision parts later on.
HaikuDepot: Use getUserRatingByUserAndPkgVersion...

... instead of searching for a rating from the given user. This API will
also return deactivated ratings, so the user could re-activate it.