Kafka Connector: Consumer Topic + Grouped Topic Support

[Kuroshii]

Changes:

• Index KafkaController instances based on both topic name and the chosen groupId for a topic this way, each different GroupedTopicSources gets it's own underlying KafkaConsumer
• If class-annotated, a TopicSource is identified by both the default groupId and it's class's name
• Add tests for the way sources are mapped

I ran all the tests locally and they all eventually passed after a rerun and 2GB of memory. Having another look at our integration tests is a good idea.

---

Please Review: @seanmrogers @dkessler-sofi @AFrieze

[dcshock]

@Kuroshii can you add a release note to the README and update the version for release? Thanks

[dcshock]

@Kuroshii is this something that we'd like to get merged in? I'm not familiar enough with the kafka connector to make the assessment.