Adding a ToolBar to the MOOSEModelBuilder's plant view. It now has the
wireframe option like the Reactor Editor version of the plant view.
Fixing a bug with the HeatExchangerController.
An incorrect value was being returned to the PlantControllerManager,
preventing the rendered HeatExchangerView from being removed from the
scene.
Updated the PlantBlockManager to add/remove plant components to/from the
plant based on their "active" flag. This syncs the rendered plant
components with the components selected in the MOOSETreeCompositeView.