Improper use of variable_get/set() and no cleanup on delete/uninstall

Protected node includes some rather worrisome use of variable_get/set().

For example:

      if ($node->show_title) {
        variable_set('protected_node-'. $node->nid .'-show_title', TRUE );
      }

This is terrible misuse of the variables table. Worse yet, if the node is deleted these variables are not cleaned up. They're also not cleaned up if you uninstall the module.

These settings should be included as part of the protected_node table and all these variables should be cleaned up from the variables table.