KeyValue Bugfix: add internal properties to blacklist, otherwise the data is added twice (eg. parent has properies and child -> child has parent + child properties instead of the aggregated data)

git-svn-id: http://www.pimcore.org/svn/pimcore/private/core/trunk@5619 1f8fe7d8-47f0-464c-8d0a-336f4953ab05