refactoring: switching to dependency injection and fixing tests

...in/java/unipotsdam/gf/modules/project/ManagementImpl.java

.../main/java/unipotsdam/gf/modules/project/ProjectView.java

...schen/src/main/java/unipotsdam/gf/session/GFContexts.java

...forschen/src/main/webapp/course/js/specificRequirement.js

...insamforschen/src/main/webapp/course/js/specificSkills.js

...nsamforschen/src/main/webapp/project/js/create-project.js

...samforschen/src/main/webapp/project/js/overview-docent.js

...amforschen/src/main/webapp/project/js/overview-student.js

...insamforschen/src/main/webapp/project/overview-docent.jsp

gemeinsamforschen/src/main/webapp/project/tasks-docent.jsp

gemeinsamforschen/src/main/webapp/project/tasks-student.jsp