Review Chapter 7.3 Object Classes

[LudwigFriedmann]

Describe your changes

Review Chapter 7.1 Introduction

• Rename "road network" to environment
• Add links from the bullet points to the class-specific sections
• Remove chapter 7.3.2

Issue ticket number and link

163

Mention a member

@ClemensLinnhoff and @FKlopfer can you briefly review and merge?

Checklist before requesting a review

• [x] I have performed a self-review of my code/documentation.
• [x] My changes generate no new warnings during the documentation generation.