HaikuDepot: Get existing rating from a user for a package
HaikuDepot: Removed invalid TODO from UserLoginWindow
HaikuDepot: Remember PackageInfoRef in PackageInfoView

 * Added getter
HaikuDepot: Now retrives existing rating for a package...

... if there is one and fills the RatePackageWindow UI accordingly.
This will allow a user to edit her earlier rating for a given package.
The button labels will need to be adjusted. Uploading a rating still not
implemented.