fix db-table-names + fix db-column-names + fix module error

.idea/misc.xml

.idea/vcs.xml

.idea/workspace.xml

notenmanager.iml

src/main/java/de/thdeg/grademanager/gui/Main.java

src/main/java/de/thdeg/grademanager/model/Course.java

...main/java/de/thdeg/grademanager/model/CoursesOfStudy.java

src/main/java/de/thdeg/grademanager/model/Enrollment.java

src/main/java/de/thdeg/grademanager/model/Lecturer.java

src/main/java/de/thdeg/grademanager/model/Student.java

...in/java/de/thdeg/grademanager/model/UniversityMember.java

src/main/java/module-info.java