[Forms] Allow textfield size to be specified

Allow specification of size per-textfield from toolbar
structure definitions; WTD-684.

platform/forms/res/templates/controls/textfield.html

@@ -4,6 +4,7 @@
                ng-required="ngRequired"
                ng-model="ngModel[field]"
                ng-pattern="ngPattern"
+               size="{{structure.size}}"
                name="mctControl">
     </span>
 </span>