[TASK] Add more infos to documentation

To the file collections part.

Change-Id: I3898beaa79a629216600bffb7a06b87482f29857
Reviewed-on: http://review.typo3.org/32264
Reviewed-by: Armin Ruediger Vieweg <armin@v.ieweg.de>
Tested-by: Armin Ruediger Vieweg <armin@v.ieweg.de>