Fixed events handling

_SelectAll_ will now only trigger "onSelectAll", as opposed to additionally trigger "onItemSelect" for every items in the list
_DeselectAll_ will now only trigger "onDeselectAll", as opposed to additionally trigger "onItemDeselect" for every items in the list

__Fixed__: "onSelectAll" was incorrectly called when clicking "Uncheck All" due to bad boolean comparison
__Added__: "Handling Events" section in the demo page