docs: Restructure of content on the AMMR page

[JacobAdamsen]

Restructuring the the order of the chapters and the content on the AMMR page according to previous talks and meetings (Bjørn and Michael).
IMPORTANT: This PR is connected to the Tutorials PR #85 "Content added from the AMMR page", where content removed from the AMMR page is being added to the tutorials at the same time.

Changes:

• The order of chapters in the content bar is changed
• Chapter "Getting Started" is removed (the content is moved to tutorial "Getting Started - first steps")
• Subchapter "Installing latest AMMR Files" removed (the content is moved tot tutorial "Getting Started - first steps")
• Subchapter "best Practices" is removed and moved to the tutorial "The AnyBody Model Repository"
• Subchapter "Ground Reaction force prediction" is moved up to be its own chapter.