Cleanup

[GPMueller]

This is some tidying up:

• improve naming and e.g. remove Hook_Pre_Iteration
• add some more const here and there
• use std::make_shared more

[codecov[bot]]

Codecov Report

Merging #627 (cffe9f8) into develop (cffe9f8) will not change coverage. The diff coverage is n/a.

:exclamation: Current head cffe9f8 differs from pull request most recent head 49821a7. Consider uploading reports for the commit 49821a7 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #627 +/- ## ======================================== Coverage 48.64% 48.64% ======================================== Files 77 77 Lines 13041 13041 ======================================== Hits 6344 6344 Misses 6697 6697 ```