Converts <ul> into interactive tree.
This converts a list into an interactive tree. Div specifies a container in which your list lives. Dir
is a directory containing important images, ext is their extension and reformat is a boolean value,
specifying whether do you want to reformat (i.e. collapse all deep levels) the tree.
Every level of resulting tree (i.e. every UL and LI) is then assigned a class name in format of
classNamePrefix_ul|li_depth
.
Example:
OAT.Tree.assign("myDiv", "images", "png", true, "myTree");