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