fix: more TaskNames are supported in tasks-student.js. Task Deadline is Timestamp now

...schen/src/main/java/unipotsdam/gf/modules/tasks/Task.java

...en/src/main/java/unipotsdam/gf/modules/tasks/TaskDAO.java

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

...insamforschen/src/main/webapp/project/js/tasks-student.js

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

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