BUG: fix memory leak of vtkIntArray related to node references

Leak was exposed by commit 21957, but was originally introduced
in revision 21810.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21966 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: disable the ChangeTracker test when the module is not available

ChangeTracker is now an extension, so it won't typically be
available when tests are being run.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21967 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Fixed memory leak in node references with events

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21968 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: fix failing test due to leaking vtkFloatArray

It is unconditionally allocated, so should be
released unconditionally too.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21969 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Added TractographyDisplay MRMLDisplayableManager and supporting changes to make possible interactive editing of fibers.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21970 3bd1e089-480b-0410-8dfb-8563597acbee
ENH: Added TractographyDisplay MRMLDisplayableManager and supporting changes to make possible interactive editing of fibers.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21971 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: fix some misc. issues with the editor identified by PNL

Thanks to Eli, Zora and all for finding these!

* 'e' key now toggles between zero and last color
* 'h' key now does not modify the Navigation mode of the crosshair
* there are now 100 undo/redo steps in the editor
* the tool palette re-docks when exiting the editor so it
will be back in place when re-entering the editor (if it had
been left undocked while editing -- space bar).

git-svn-id: http://svn.slicer.org/Slicer4/trunk@21972 3bd1e089-480b-0410-8dfb-8563597acbee