Default options form that provides the label widget that all fields should have.
Overrides FieldPluginBase::buildOptionsForm
public function buildOptionsForm(&$form, &$form_state) {
$form['text'] = array(
'#type' => 'textfield',
'#title' => t('Text to display'),
'#default_value' => $this->options['text'],
);
parent::buildOptionsForm($form, $form_state);
}