Automagically run a script to update our sandbox asset dates daily

[ToddKerpelman]

This is a python script that...

1. Looks through our two Asset Sandbox user json files
2. Finds the most recent date in these files
3. Sets that date to today, and then scales all other dates proportionately

And then we have a workflow script that, in theory, runs this script once a day and commits the result.

I'm keeping this limited to assets for now, just so we can limit the damage in case something goes wrong.

[ToddKerpelman]

(I should note this PR also includes what those two files look like after running the script_