Revision of all episodes

We should revise all episodes in accordance to the following checklist:

• Every episode should have an "Overview" and a "Key Points" section.
• Check to use only use common markdown features if feasible. If we use special check boxes or other features we need to make sure that it looks fine on the website and in the pad.
• Always use 4 spaces for indented lists.
• For unordered lists we should use - instead of *.
• Apply the one sentence, one line principle consistently.
• Links need to have explicit Markdown link syntax