Add a listener to rename content sub-pages when corresponding version name is changed

For a versioned page, the sub-page containing the content for a version is named after the version page's name. For instance, if the version "Version 3" page is named "v3", the sub-page of the "myPage" will be "myPage.v3".

A listener has to be created, to handle the case where a version page is moved in the same book (renamed). When a change is detected, this listener has to rename all the corresponding sub-pages, or the content would be lost.