Issue #1623534 by jayaram: Modified how we get the language of for a dummy form so that it will not cause a notice for some entities.

Added widget settings to button_field_field_widget_info() and removed extraneous empty/isset checks.

Issue #1587382 by ditcheva: Fixed additional class and hide on edit not reflecting their value properly on widget settings form.

Added dummy form to use when viewing the field so that we can still utilize Drupal's ajax framework.