gamefactorys, little bugfixes+optimisations+cleanup
Merge branch 'oauth2' of github.com:LearnPhysics/WebApp-PhysixLab into oauth2

Conflicts:
	src/main/java/de/hofuniversity/iws/client/widgets/Thema/Lektionswahl.java
	src/main/java/de/hofuniversity/iws/server/XMLReaderParser.java
	src/main/java/de/hofuniversity/iws/server/services/LessonServiceImpl.java
	src/main/java/de/hofuniversity/iws/shared/dto/LektionDTO.java
	src/main/webapp/Subjects/kinetic/lessons/pendulum/lesson.xml