Further improve documentation

[HenrZu]

Provide a description of requested documentation changes.

After merging #1338 , this Issue/branch is used to further improve the documentation. After enough changes are done, this will be merged.

[reneSchm]

There seem to be issues with python/coupling_sbi.rst and python/coupling_sensitivity.rst:

memilio/docs/source/python/coupling_sbi.rst:17: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:63: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:79: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:86: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:87: WARNING: Block quote ends without a blank line; unexpected unindent.
memilio/docs/source/python/coupling_sbi.rst:95: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:96: WARNING: Block quote ends without a blank line; unexpected unindent.
memilio/docs/source/python/coupling_sbi.rst:100: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:107: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:109: WARNING: Block quote ends without a blank line; unexpected unindent.
memilio/docs/source/python/coupling_sbi.rst:170: ERROR: Unexpected indentation.
memilio/docs/source/python/coupling_sbi.rst:171: WARNING: Block quote ends without a blank line; unexpected unindent.

Also

memilio/docs/source/python/coupling_sbi.rst: WARNING: document isn't included in any toctree
memilio/docs/source/python/coupling_sensitivity.rst: WARNING: document isn't included in any toctree

[kilianvolmer]

Also

memilio/docs/source/python/coupling_sbi.rst: WARNING: document isn't included in any toctree
memilio/docs/source/python/coupling_sensitivity.rst: WARNING: document isn't included in any toctree

They are preliminary files and belong to #1389

[reneSchm]

They are preliminary files and belong to #1389

"Preliminary files" must not be merged into main. It is important to keep the main clean of development artifacts, this includes documentation. Please avoid this in the future.