Caf:PdmUiTree: Rewrote rebuildUiSubTree to become updateUiSubTree
Now the UI state is preserved when refreshing the tree, making it suitable
to use this method more extensively. This paves the way to make changes to the Pdm data structure without considering the ui at all, until a  call to updateUiSubTree gets the ui gracefully into sync.
p4#: 21599