catch NullpointerException on fileSize.toString()
dynamic administration of contentmodels aka transformers
Merge branch 'EDOZWO-190' into 0.2.0

Conflicts:
	regal-api/src/main/java/de/nrw/hbz/regal/api/Utils.java
	regal-api/src/main/java/de/nrw/hbz/regal/api/helper/Actions.java
first tested version with one content type per transformer