Consistency of (main) adapters overviews

Of the 7 "main" adapters, 4 of them have more than one page: CalculiX, SU2, OpenFOAM and deal.ii. However, each has a different structure. A common structure would be welcome.

Some spotted issues & fixes:
- Only deal.II describes the original solver. (SU2 in part) **=> Add "What is CalculiX?" and "What is OpenFOAM?"?**
- History / references / cite section inconsistent, and empty with deal.ii (add the citation from the repo README : https://github.com/precice/dealii-adapter ?) **=> Make a References section with (if any) history + a "related literature" subsection?**
- "What is this" with OpenFOAM and SU2 => Split with "What is [solver]?" and "What is the adapter?" (Latter: plug-ing ? Standalone program? Different program)
- CalculiX has a "start here" section linking to other pages (build, configure, tutorials). Same for OpenFOAM and SU2 but it's called "Try". **=> Rename CCX one to "Try"?** For deal.ii it's... Chaotic. Move things into a section that references new pages?

Suggested overall structure

- What is [solver name]?
- What does the adapter do/ what is it? (i.e. a plugin, a standalone app, a library, ...) **Unsure about the title**
- - Also include supported versions there?
- Usage
- - Links to get/build/configure/run tutorial pages
- - For deal.ii, also links to limitations, assumptions, theory, etc
- References / history / cite

Draft PR planned on my side but agreement on structure first would be better.

EDIT: some checkboxes:

- [ ] Consistent introduction: 1) what kind of solver is this? 2) What kind of software is the adapter ?
- [ ] Is the next section (commong name? "Try" ? "Get started" ?) introducing links to build/configure the adapter.
- [ ] Are there links to (main?) tutorials showcasing this adapter?
- [ ] Is the references section at the end consistent with others? The OpenFOAM one seems like a nice template. (Different font for references)