[Documentation] Content of the documentation

[FredericHirschmueller]

The following content is ranked by priority from the stakeholder:

1. Step by step guide to the use of the tool
2. Detailed description of example projects
3. Detailed model description (Equations)
4. Simple explanation of the mathematics behind the tool
5. Description of the open_plan project

[mstich0]

@FredericHirschmueller That is done right?

[FredericHirschmueller]

I think we can marc this issue as done, since we added a lot of documentation at the end of the last project. I will do that now.