Changes

Summary

1. switch to make or not make feature blocks optional over paramter (details)
2. better handling of empty answer dataframe (details)

Commit bdfd366a94ded7d0aa026b7ab2604032d1840a02 by carsten.draschner switch to make or not make feature blocks optional over paramter
	sansa-ml/sansa-ml-spark/src/main/scala/net/sansa_stack/ml/spark/featureExtraction/FeatureExtractingSparqlGenerator.scala (diff)
Commit 943150cca1579a94db2fb98620cf9114c80908d0 by carsten.draschner better handling of empty answer dataframe
	sansa-ml/sansa-ml-spark/src/main/scala/net/sansa_stack/ml/spark/featureExtraction/SparqlFrame.scala (diff)