Sets the selection model, which must be one of
TreeSelectionModel.SINGLE_TREE_SELECTION,
TreeSelectionModel.CONTIGUOUS_TREE_SELECTION or
TreeSelectionModel.DISCONTIGUOUS_TREE_SELECTION.
Deprecated.This method no longer returns a shared instance, as it
caused problems with one view setting properties (such as enabled
state) on the renderer and the renderer then being used in its altered
state by a different view. Views should create their own instance of
NodeRenderer instead.