take over the changes from master

Closes #430 (closed), #429 (closed), #414 (closed), #427 (closed)

This takes over all commits from master that weren't related to vectorized systems. Additionally it includes extra updates, listed in the comment below.

So far I just took over all commits and merges as listed in #430 (closed). I didn't verify the correctness of the code, and some things are bound to fail. I also made some empty commits for simpler book-keeping (I wrote a script to take care of migration, and it was easier to do this way).

Here's also a map master_sha -> main_sha together with a status of the cherry-picking (whether it resulted in a conflict).migration_log.yml. This was generated using this script:migration_plan.py. The commits that I took over are documented in migration_plan.yml.