PHOT-20: web service to add images to collection.
Merge remote-tracking branch 'origin/PHOT-20' into PHOT-20

Conflicts:
	src/main/java/de/htw/sdf/photoplatform/webservice/controller/PhotographerController.java
	src/main/java/de/htw/sdf/photoplatform/webservice/dto/CollectionData.java
PHOT-20: fix merge conflicts