Fix for U4-3831.  

It appears the add button (`<input type="submit" />`) is submitting the entire page, rather than just calling `add()` on the containing form.  This makes it impossible to add items in some browsers.  This commit removes the containing form, changes the submit button to just a `<button />` and adds `ng-click` with `$event.preventDefault()` to prevent submitting the entire page.