Finish chapter "Customizing your Inspector"

[koendehondt]

Open issues from https://github.com/SquareBracketAssociates/BuildingApplicationWithSpec2/pull/65:

• [ ] There was no section on the breakpoints tab. I added the section header, but no content. Let's decide what to do with it.
• [ ] 2 figures are GIFs. That does not work. We need an alternative.
• [ ] The text mentions "small grey rectangles at the bottom of the window", but no figures are showing that. Adding it will require generating all the figure files again.