Start correct use case + correct env variables

u-number inside Application properties

 + Moved samza-standalone-properties in every folder arcorrdingly

Split record generator and sender in load generator

Closes #280

See merge request !203

Upgrade PMD and Checkstyle versions

See merge request !188

Just in usecase 4 for now

delete Uc4ApplicationBeamNoFeedback

The pareents are used as state

refactor uc4-beam a bit

refactor + use Generalized KafkaReader and writer

Also excption Exception in thread main java.lang.IllegalArgumentException:
 Cannot union streams of different types:
  CoderTypeInformation{coder=WindowedValue$
  FullWindowedValueCoder(KvCoder(NullableCoder(StringUtf8Coder)
  ,org.apache.beam.sdk.coders.AvroCoder@b03f3cea),IntervalWindow)}
  and
  CoderTypeInformation{coder=WindowedValue$
  FullWindowedValueCoder(KvCoder(NullableCoder(StringUtf8Coder)
  ,NullableCoder(org.apache.beam.sdk.coders.AvroCoder@b03f3cea)),IntervalWindow)}
 by just using the raw not NullableCoder

settings.gradle + build.gradle + Changes to KafkaReader