Wrap known Data Names in relevance with ${}

[yanokwa]

I think this might be hard thing to fix, but figured I'd file it.

Given a form that uses the "or other" option, the logic that gets exported to XLSForm isn't correct.

• Untitled Form.odkbuild.zip
• Untitled-Form-export.xlsx

In the relevant column of favorite-color-other, I expect (selected(${question}, 'o')), but I get (selected(question, 'o')).

The Data Name should be wrapped with ${}. The path doesn't matter because pyxform requires that the Data Name to be unique.