Provide an "Any Value" option as a trigger for controlling fields

Issue Summary

It would be nice to be able to control a field if any value is chosen for a controller that has optional input.
I suggest adding an option (under "not conroled") that says "Any Value".

so no selected value would hide, and any selected value would show.

i realize you can select all options on the settings form, but when using select lists that draw their input from elsewhere (content taxonomy), new items can be added by other admins, thus leaving them unchecked in the conditional fields config form.