A teacher can password protect a lesson and/or set available from and deadline dates

1. Login as a teacher, update a lesson, set 'Password protected lesson' to yes and enter a password.
2. Login as a student and check that you are prompted to enter a password before being allowed to access the lesson.
3. Login as the teacher, update the lesson and set an 'Available from' date in the future.
4. Login as a student and check that the 'Available from' date is displayed in the lesson and in the course calendar, and that it is not possible to access the lesson.
5. Login as the teacher, update the lesson, disable the 'Available from' date and set a deadline in the future.
6. Login as a student and check that the deadline is displayed in the course calendar and on the site index page.