Implements Active document containment.
In MFC, an Active document is handled similarly to a regular, in-place editable embedding, with the following differences:
The COleDocument-derived class still maintains a list of the currently embedded items; however, these items may be COleDocObjectItem-derived items.
When an active document is active, it occupies the entire client area of the view when it is in-place active.
An Active document container has full control of the Help menu.
The Help menu contains menu items for both the Active document container and server.
Because the Active document container owns the Help menu, the container is responsible for forwarding server Help menu messages to the server. This integration is handled by COleDocObjectItem.
For more information on menu merging and Active document activation, see Overview of Active Document Containment.