Use new API-Calls

[RedTo]

The API has changed. Integrate the new one as follows:

• https://nine.wi.hm.edu/api/v2/apps/cie/courses/WiSe%202018 (All courses of semester, for example WiSe 2018)
• https://nine.wi.hm.edu/api/v2/apps/cie (get all semesters of cie)
• https://nine.wi.hm.edu/api/v2/courses/subscriptions
• https://nine.wi.hm.edu/api/v2/courses/subscripe
• https://nine.wi.hm.edu/api/v2/courses/unsubscripe
• https://nine.wi.hm.edu/api/Lecturer/GetAllLecture

[RedTo]

• https://nine.wi.hm.edu/api/Lecturer/GetAllLecture (already in use)
• https://nine.wi.hm.edu/api/v2/courses/subscripe (already in use)