Make livedata's edit mode better integrated in XWiki's UI

It should be easier to enter edit mode in a livedata (right now, it requires toggling a checkbox in the livedata's dropdown menu).

Ideally, a user should be able to access it by simply clicking the edit button in a page in view mode. Also, they should have optional access to a maximized view, allowing them to focus sorely on the livedata's content.