Port image entrypoint scripts to Python

[robertbartel]

People keep bashing our shell scripts, though it has bo[u]rne out to be more difficult to maintain these, especially collaboratively.

We already have #560 to port the utility scripts. It probably makes sense to nix the current Docker image entrypoint scripts also and replace them with Python versions.

[robertbartel]

It might make sense to do this and #174 at the same time.

[christophertubbs]

People keep bashing our shell scripts, though it has bo[u]rne out to be more difficult to maintain these, especially collaboratively.

sudo pkill badpuns

Utilizing entrypoint.sh is probably still good, but any sort of fanciness beyond simple one-liners could probably be farmed out to easy to follow python scripts.