Chapters 5, 12 and 15, updates to 7, and clean-out of chapter 3

What's Changed

• chapter 15 - data ethics by @campbelle1 in #38
• Adding draft of Chapter 12 by @amandakube in #37
• Reformatting Control Statement Chapter by @SusannaLange in #39
• Change to toc ch3 by @amandakube in #40

Full Changelog: 0.12.0...0.13.0