Select: support required (but initially unset) fields

[bill]

Add way to make select widgets initially have "no value" but then require the user to pick something from the drop down. The drop down shouldn't include a blank option as a value.

<select dojoType="dijit.form.Select" value="" required="true">
	<option value="TN">Tennessee</option>
	<option value="VA">Virginia</option>
	<option value="WA">Washington</option>
	<option value="FL">Florida</option>
	<option value="CA">California</option>
</select>

I thought Nathan said this was already supported but it doesn't seem to work for me. Maybe it works when loading from an external store but not from inlined data?

Split off from #10431.

[Douglas Hays]

This would ideally require an invalid icon added to the template.

[dylan]

Given that no one has shown interest in creating a patch in the past 5+ years, I'm closing this as patchwelcome.