`KafkaRecordSender` does not only support sending Avro values in combination
with the Confluent Schema Registry anymore, but also arbitrary other
types using a custom serializer.

new output: AggregatedPowerRecords
refactoring: remove inferable types
set id in combine function of aggregator

Add Beam Kubernetes Benchmark Definitions

See merge request !218

Align package structure among all benchmark implementations

Closes #310

See merge request !249

Merge branch 'refactor-beam-service' of git.se.informatik.uni-kiel.de:she/theodolite into refactor-beam-service