[StatusView] Fix leaks.
[Tasks] Fix leak in CommentTasks.
[SdiWorkspace] Fix subview not being disposed.
[MainToolbar] Remove dangling event attachment.
[PadTreeView] Correct call to base function.
[MainToolbar] Make last command target a weak ref.
[CommandMenuItem] Make last command weak ref.
[ProjectPad] Also clean current item.
[MainToolbar] Use args to get new item.
[ExtensibleTreeView] Don't cache navigators. They keep references to data items and the GC cannot collect Solutions for instance.
[VersionControl] Use a weak reference when caching StatusView items.
[NavigationHistory] Clear closed history.
[NUnit] Fix leak of UnitTestCollection.
[RootWorkspace] Switch order of first/last open/close events.

It makes sense to have FirstWorkspaceItemOpened before WorkspaceItemOpened.
Same for LastWorkspaceItemClosed to happen after WorkspaceItemClosed.
Fix issues reported in PR for leaks branch.
Revert NUnit changes.
Fix TIE in VersionControlCommandHandler.
[CommandMenu] Replace with a better fix.
[ExtensibleTreeView] Reset nodes instead of creating new ones.
[MainToolbar] Fix TIE in lastCommandTarget.