Gets the behavior setting of an specific plugin.
string $plugin_id: The plugin ID for which to get the settings.
string|array $key: Values are stored as a multi-dimensional associative array. If $key is a string, it will return $values[$key]. If $key is an array, each element of the array will be used as a nested key. If $key = array('foo', 'bar') it will return $values['foo']['bar'].
mixed $default: (optional) The default value if the specified key does not exist.
mixed The value for the given key.
public function &getBehaviorSetting($plugin_id, $key, $default = NULL);