Merge branch 'refs/heads/dev' into dev_zip_files

# Conflicts:
#	CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/datastructure/LibraryObject.java
#	CityDoctorParent/CityDoctorModel/src/main/java/de/hft/stuttgart/citydoctor2/mapper/citygml3/Citygml3FeatureMapper.java
#	CityDoctorParent/CityDoctorValidation/src/main/java/de/hft/stuttgart/citydoctor2/check/Checker.java
#	CityDoctorParent/Extensions/CityDoctorGUI/pom.xml
#	CityDoctorParent/Extensions/CityDoctorGUI/src/main/resources/de/hft/stuttgart/citydoctor2/gui/MainToolBar.fxml
#	CityDoctorParent/Extensions/CityDoctorHealer/pom.xml
#	CityDoctorParent/pom.xml