AnchorPane::set(Bottom,Left,Right,Top)Anchor method mentions that "Setting the value to null will remove the (anchor) constraint."

The expectation is that clearing the anchor constraint should re-position the node to an un-anchored state, but the node remains in its anchored location.

To reproduce:

- run the attached code
- click [Set Anchors] button
- observe the node moving to the proper location and its properties updated (pane-XXX-anchor) (correct behavior)
- click [Clear Anchors] button
- observe properties cleared (correct behavior)
- observe the node remaining in its anchored location (INCORRECT behavior)