[TASK] Remove: Open Documents module

Removes the Module Menu item for OpenDocs on the left.
Also moves Css/JavaScript/Images and Icons to default folders.

Change-Id: I90c3f04f5981c6b0e02b036c8b604ce03b3d7b66
Fixes: #41240
Releases: 6.0
Reviewed-on: http://review.typo3.org/15107
Reviewed-by: Helmut Hummel
Reviewed-by: Mattias Nilsson
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn