- added new CSS state class to each visible item: 'aciTreeVisible' and for hover (on the 'aciTreeButton' and 'aciTreeLine'): 'aciTreeHover';
- new core API method: .visible (to filter out only visible items), .isOpenPath to test if the path to item is open;
- added new class to all visible elements: 'aciTreeOdd' / 'aciTreeEven' so now is possible to format
the selection, columns etc. for odd/even rows;
- CSS fix for item width vs. 'overflow:auto' - changed to 'hidden' (to clear the floats when using
the columns);