Add user_input_date function

There are a few scripts now that collect instrument data for manual tests. it would be good to have a date validator that can be used across the existing and any future scripts.

For the GUI would be nice to be able to use an actual date picker.
For the CLI, something like what I've done recently (come see me if you don't know, don't want to mention work specific things in the opensource land - that is, if it's not me that adds this feature).