Semantic UI SelectWidget Should Support Labels

[amerryma]

Reasons for making this change

The semantic ui select widget does not allow for labels on the dropdown. Without it, there is no way to tell which field is being edited. Other UI components already do this.

See example here.

Checklist

• I'm updating documentation
  • I've checked the rendering of the Markdown text I've added
• I'm adding or updating code
  • I've added and/or updated tests
  • I've updated docs if needed
• I'm adding a new feature
  • I've updated the playground with an example use of the feature

[epicfaace]

Thanks, can you add a snapshot test that uses a label?

[jacqueswho]

@amerryma you do know this is not going to look right? Semantic ui does not use a label for drop down but the select control?
see example form dropdown .

[epicfaace]

@jacqueswho I think #1972 already takes care of this issue, so are you good with closing this PR?