Improve lecture descriptions

[LeonMatthes]

Possible improvements include:

• Linking more methods and classes for easier navigation
• Check for "advanced" terminlogy that a newcomer might not understand
• Clearly state the goals of the lectures

[LeonMatthes]

Started reworking the lecture descriptions
New rules for formatting the lecture descriptions:

• The first line is the title and bold
• Add a new line after a
  tag to reflect later HTML formatting
• Link any classes/methods that are relevant for the lecture
• Code snippets should be surrounded by double quotes " and be italic (ex.: "Morph new")
• If appropriate, add an empty line between additional information and the lectures acceptance criteria

This also means removing any left italics formatting from class names, which was inconsistent anyway

[LeonMatthes]

Linking and clear goal statement have been adressed.
Should check with Squeak newcomers for advanced terminology as it is difficult to judge without more information about the target group