content definition filter rules refactored

no more JSON or nasty strings like: \\\"name\\\"... when adding filter rules

@tkolhar @hhovsepy please look at you tests just to be sure I have not broke them
(ConsumeFilteredPackageGroup, ConsumeFilteredPackage, ConsumeFilteredErrata)

new FilterRule... classes added to com.redhat.qe.katello.base.obj.helpers package because filter rules are not real katello objects