Add specialized short-form string/line type

This is to help differentiate between <input type="text" /> and
<textarea> fields. We need this for UploadWizard in particular because
we intend to build a form for the Information template on Commons, and
it has both small fields (for which we'll use <input>) and big ones
like description (for which we need <textarea>).

Change-Id: Ib9b381816d18f2723a9f715c54f6a64ff4b69847
Merge "Add specialized short-form string/line type"