* @cfg {string} tooltip Text for the tooltip
* @cfg {string} container_method method to fetch parents container element (used by NavHeaderbar - getHeaderChildContainer)
* @cfg {string|object} visibilityEl (el|parent) What element to use for visibility (@see getVisibilityEl())
* @cfg {string} tooltip Text for the tooltip
* @cfg {string} container_method method to fetch parents container element (used by NavHeaderbar - getHeaderChildContainer)
* @cfg {string|object} visibilityEl (el|parent) What element to use for visibility (@see getVisibilityEl())