Move Topic and User Operators back to v1beta1 to allow downgrades

We originally decided to use v1beta2 resources in User and Topic Operators. This was because when upgrading to 0.23, the v1beta1 version would not be available which would result in deleting the topics (Fabric8 treats HTTP 404 as resource does not exist which tricks the operator into thinking that the KafkaTopic or KafkaUser resource does not exist anymore). However, this obviously screws up the downgrade.