Lecture notes updated with exercises

The lecture notes are now updated. There is now a lot of material from Chapter 3, but you do not need to look at it yet. Now you can find the exercises from Chapter 3 and you are ready to solve any exercise from 3.1 to 3.12. Solve those that you manage or have time to.

From yerterday's lecture I have added a deeper discussion into the topic of completeness of measures. However, I prefer that you solve the exercises.