provide cache controll for several responses

Add Cache-Control headers to all listed functionalities:
- News: uncached
- Canteen: 7d /Overview (30d)
- Mail: uncached
- info/XXX: 10d
- timecal: 1d
- QIS: uncached
- Rooms: uncached

```
(...., HttpServletResponse response)
response.setHeader("Cache-Control","no-store, no-cache, must-revalidate");

Cache-Controll: public, max-age: TIME_IN_SECONDS
```
