Add Support for Apache Kafka

Besides the following processing platforms:

[Java 8 Streams]
[Apache Spark](https://spark.apache.org/)
[GraphChi](https://github.com/GraphChi/graphchi-java)
[Postgres](http://www.postgresql.org/)
[SQLite](https://www.sqlite.org/)
[Apache Flink](https://flink.apache.org/)

it is suggested to also support Apache Kafka.

This issue is considered to be an umbrella for other issues, related to that topic. I expect it to be open for some time, until we can say: Apache Wayang supports Apache Kafka as a processing platform (even if today it is not yet 100% clear in which scope that will be)