TreeView changes integrated into 2.1-b39-controls-scrum build introduced memory leak in TreeView.

This lead to max memory usage growth in Controls.TreeView-Expand benchmark
and following NodeMemory regressions:

- NodeMemory.TableView
  96%: 811,970 => 33,470
  
- NodeMemory.TreeItem
  22%: 63,240 => 49,440


Steps to reproduce memory leak in TreeView:
> javac -cp "rt/lib/jfxrt.jar" TreeViewExpandPerfTest.java
> java -Xmx16m -cp "rt/lib/jfxrt.jar;." TreeViewExpandPerfTest


controls-scrum build #39 changes are:
1. Automated merge with ssh://jfxsrc.us.oracle.com//javafx/2.1/scrum/controls/jfx/runtime (detail)
2. Re-enabling most, but not quite all, VirtualFlow unit tests that were @Ignore'd at the class level. (detail)
3. RT-17828: NPE in TableCell when TableView.items is null (detail)
4. [TEST ONLY] Add TreeView unit test to ensure selection remains where it is expected to remain when a branch is expanded (detail)
5. RT-17686: The preferred width / height of an empty table should be a golden ratio. (detail)
6. RT-17095: TreeView: selection issues (detail)
7. RT-16565: TreeView: wrong return of treeView.getSelectionModel().getSelectedItem() (detail)