Restructure quickstart

[davidscn]

Open TODOs:

• update README
• update image (essentially an older TODO)

[davidscn]

Ready for review, but still in draft in order to avoid an accidental merge.

[uekerman]

Please remember to not merge this before everything else is merged. Otherwise we change the content here: https://www.precice.org/quickstart.html
The webpage points to the restructure branch.

[MakisH]

A few minor comments, mostly very picky changes in the formulations and a rather important bug prevention in the scripts.

I ran the case and I observed that:

• ✔️ The case is running
• ❌ The removeObsoleteFolders.sh needs to remove the cd Fluid and the cd ...
• ✔️ The plotDisplacement.sh works
• ✔️ ParaView works.
• ❔ I still see a kind-of "explosion" in the second half of the simulation (higher-frequency oscillation). Maybe we could add a note that this is expected and why.
• ❌ clean.sh needs a few fixes (see review)

Looks very nice already! 🚀

[MakisH]

A few more minor changes in the README.md (sorry, I only saw them now)

[davidscn]

I added now a result figure. Feel free to comment on it. Other than that, the PR should be ready.

[MakisH]

Please remember to not merge this before everything else is merged. Otherwise we change the content here: https://www.precice.org/quickstart.html
The webpage points to the restructure branch.

Just a reminder

[davidscn]

@MakisH merging develop was a bit of a challenge. but you can cross-review the cleaning/running now as discussed.

[MakisH]

I looked at the commit with the cleaning/running and the latest state and it looks good 👍.