UPDATE:
all callbacks are fired within the tree scope (this is a reference
to the tree instance)
added _create, _rename, _remove, _load_branch
changed oncreate, onrename, onremove callbacks
static becomes staticData
fixed oncreate callback to fire AFTER the node is renamed
fixed JSON datastore get method
fixed multilanguage in IE8
context menu plugin - removed flicker on two consecutive right
clicks
added repair function to checkbox plugin to handle move/copy/create/
delete