Carefully revise Quickstart document

This document is far from ready to be published. I went over some obvious mistakes like empty markdown cells and some other orthographic errors.

Please consult with Valentin about this before publishing it. I think the process as you currently describe it doesnt work; You center the meshes AND suggest to adjust the transform? That will not work imo.

Originally posted by @maxrohleder in https://github.com/maxrohleder/ReMAS/pull/41#pullrequestreview-1020971385