HaikuDepot: Clean up how PackageInfo is populated

 * Remove the stuff from constructor, which cannot be known at the time
   (icon and changelog).
 * Added setters for those and notification handling (not yet in the
   listeners).
 * Add more PackageInfoListener flags.
 * Populate categories and dummy user ratings for "wonderbrush". This
   code was still in from testing, but the package name is actually
   different in real PM.
HaikuDepot: Update the correct view for given notification