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

TemplateDataBlob.php

@@ -69,6 +69,7 @@ class TemplateDataBlob {
 			'number',
 			'string/wiki-page-name',
 			'string/wiki-user-name',
+			'string/line',
 		);
 
 		if ( $data === null ) {

spec.templatedata.json

@@ -48,6 +48,8 @@
 	- string/wiki-user-name
 	  A valid MediaWiki user name for the current wiki. Doesn't have to exist,
 	  but if not should be a valid user name to create.
+	- string/line
+	  Short text field - use for names, labels, and other short-form fields.
 
 @structure {string|Object} InterfaceText
 	A free-form string (no wikitext) in the content-language of the wiki, or,