- adds missing header to files
- unify header
- add SPDX (https://spdx.dev/) identifier to header (first step for getting REUSE https://reuse.software/ compliant)
- reworked doxgen

- uses awesome doxygen theme: https://jothepro.github.io/doxygen-awesome-css/

Adresses: #183

- adds wiki pages to doxygen page
- adds doxygen modules for production code and tests

Update virtualFluids python requirements to fit python3.11. Remove VTK. Outcomment unused python test from Sven.

This fixes incorrect times in the logger output.

Using ENV for DEBIAN_FRONTEND is deprecated: https://github.com/moby/moby/issues/4032

Adds python dependency to vf dockerfile and removes the redudant docker file, as singularity is not need anymore here. Adjust the CI.