Update dev

See merge request !9

Version 3.15.0

See merge request !8

# Conflicts:
#   CityDoctorParent/CityDoctorCheckResult/pom.xml
#   CityDoctorParent/CityDoctorEdge/pom.xml
#   CityDoctorParent/CityDoctorEdge/src/main/java/de/hft/stuttgart/citydoctor2/edge/PolyLine.java
#   CityDoctorParent/CityDoctorModel/pom.xml
#   CityDoctorParent/CityDoctorValidation/pom.xml
#   CityDoctorParent/pom.xml

Gitlab changelog and templates

See merge request !7

Slight adjustment of null line check to account for intersection lines of
vertex-to-polygon intersections.

Added a function for the generation of TestCases during debugging for
quicker analysis of false positive self-intersections.

Open source release of CityDoctorGUI and other extensions.

See merge request !6