[TASK] Drag&Drop of Content-Elements in Page-Module

Change-Id: I1fca2b537f134b57f3161d6ae636c6d9e67012e0
Resolves: #17198
Releases: 6.0
Reviewed-on: http://review.typo3.org/15103
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel