Password text fields (hides user input).

1. Example 1: Basic Password Field

   add_action( 'fm_post_post', function() {
   	$fm = new Fieldmanager_Password( array(
   		'name' => 'demo-password',
   	) );
   	$fm->add_meta_box( 'Password Field', array( 'post' ) );
   } );