Fixed erroneous instantiation of component views by top-level desktop hosts.

* Added ComponentView properties to the four top-level desktop hosts (DialogBox,
  Shelf, Workspace, WorkspaceDialogBox).
* Fixed the views of the four top-level desktop hosts to use the ComponentView
  property instead of instantiating their own *throw-away* copy of the view,
  thereby setting the stage for a second component view to be created at a later
  time when the component host's ComponentView is accessed.

Fixes #23
Fixed merge errors