Change no-argument behavior to displaying help, add --load-cache argument

[D-Vaillant]

It's kind of counter-intuitive for the no-argument behavior to do something. We can shift that to a --load-cache argument which runs the loading if we ask for it.

A related suggestion: Add --cache/-c which caches whatever command we enter. That way one could set a baseline, mess around with some options, and then revert back to their cached setup (instead of the way it is now, where the last-used arguments are cached.)

I can probably add this into the argparse pull request without much difficulty since it's mostly just adding on some if-thens.