Support UI for Update Container for Experience Pages which also have inherited Containers

In CMS-13325 we added that container items can only be moved within the XPage containers and not to inherited HST Config containers. The reason is related to access rights (user roles) and even more fundamental, that XPage and HST Config containers have their own preview/live lifecycle.

In the CM UI, we have to make sure that it is clear that for an XPage you cannot move container items between XPage and HST Config.

Discussed so far: 

• The user is either editing the containers on the actual (X)Page or its inherited containers.
• In the UI the term 'shared containers' will be used, as inherited containers are shared by multiple pages.
• If the user is allowed to edit both page containers and shared containers, the shared containers are disabled initially (dotted outline, no component outlines). The user can switch between editing the page container and editing the shared containers, using a button in the overlay (the page containers get the disabled appearance). And back using a button in the notifications banner or on the page in the overlay.  
• For users that are authorised to edit the layout of XPages only. The overlay shows only page containers (and components); no outline for shared containers.
• It is clearly indicated to the user what type of page he is on: 'Classic page' (HSTpage) or 'XPage'