[Property Sections] Improve method to filter object
ToggleViewAction should not activate view
[TreeStateHelper] Fix expanded tree node state not restored when opening Model View

* This was OK in Eclipse 3
* In Eclipse 4 check flag
[Menus] Add menu placeholders
[EditorModelManager] Don't call getModels() when checking dirty on close

* If the Model Tree is not open when opening the app, models will not be loaded
* So, when closing the app we don't want to re-load them!