Chapter/sub-chapter numbering for 5 & 5.1 is wrong

[UweSauter]

Heading in chapter 5 reads "5.1. Summary of Steps" and heading in chapter 5.1 reads "5.2. The target specification JSON file", probably related to #33 .

[UweSauter]

Also, heading of chapter 6 reads "5.2. Quick start from template"

[stappersg]

There is a commit for "5.1", none yet for "5.2".