[Controls] pass item as structure

Pass the item to child controls inside of a composite instead of
the row object.   Thus, options are correctly passed to children.

Fixes #1785.

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

@@ -27,7 +27,7 @@
                          ng-required="ngRequired || compositeCtrl.isNonEmpty(ngModel[field])"
                          ng-pattern="ngPattern"
                          options="item.options"
-                         structure="row"
+                         structure="item"
                          field="$index">
             </mct-control>
             <span class="composite-control-label">