Merge branch 'task-implementation-course' into 'master'

.../ui/cs/advprog/tutorial0/controller/CourseController.java

...rog/tutorial0/exception/DuplicateCourseNameException.java

...main/java/id/ac/ui/cs/advprog/tutorial0/model/Course.java

.../ui/cs/advprog/tutorial0/repository/CourseRepository.java

.../id/ac/ui/cs/advprog/tutorial0/service/CourseService.java

...ac/ui/cs/advprog/tutorial0/service/CourseServiceImpl.java

src/main/resources/templates/courseList.html

src/main/resources/templates/createCourse.html