Content added from the AMMR page

[JacobAdamsen]

This PR is connected to the AMMR PR #1121 "Restructure of content on the AMMR page", so these should be merged at the same time.
Some chapters and content on the AMMR page is rearranged, and some of the content is moved from the AMMR page to the tutorials.
Note: the test gives error "broken link: https://anyscript.org/ammr/grf_prediction/grf-prediction.html" - this link will only be created when the AMMR PR #1121 is merged

Changes:

• Content from AMMR chapter "Getting Started" is added to tutorial "Getting Started - first steps"
• Content from AMMR subchapter "installing latest AMMR files" is added to tutorial "Getting Started - first steps"
• Content from AMMR subchapter "best Practices" is added to tutorial "The AnyBody Model Repository" as new chapter