Some styling rules are not applied when Hierarchy panel is used outside of SceneBuilderApp

Look at the attached snapshots:

1) InsideApp.png shows Hierarchy panel in Scene Builder App
    => custom expand/collapse icons are displayed
2) OutsideApp.png shows Hierarchy panel in SceneBuilderSWT sample
    => default expand/collapse icons are displayed
    => some styling rules have not been applied : BUG

Note 1: the same is observed with SceneBuilderSW (Swing integration).

Note 2: the drag visual is also buggy ; in InsideApp.png, visual is the
object class icon ; in OutsideApp.png visual is a blank square ;
this is likely to be an issue in FX (to be confirmed).