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['extension_detect_tar'] = array(
'#type' => 'checkbox',
'#title' => t('Detect if tar is part of the extension'),
'#description' => t("See if the previous extension is '.tar' and if so, add that, so we see 'tar.gz' or 'tar.bz2' instead of just 'gz'."),
'#default_value' => $this->options['extension_detect_tar'],
);
}