Radio button fields need a "clear" option

[jeremydw]

Once I make a choose something with a radio button, I can't clear it out without editing the source. The workaround in the meantime is to have a superfluous "None" radio button -- but ideally we should have a way to "clear" the field.

[adelaidemt]

I kind of think it should be kept in, and if not needed, the user selects "none". We could also change "None" to "N/A"?

[jeremydw]

The issue is "None" is a manually coded value in the schema. I think we need an inbuilt "X" (similar to the one that shows up in variations) that allows the value to be fully cleared out (just like variations).

[Zoramite]

We can add a clear option built into the field, but to make the UX better we should ensure the field validation does not require the field before showing the 'clear' option.