[DOC] Improve Documentation for 3.0 release

Change-Id: I51115d17e40319f8f2cf00fac5acae45ccd54414
Reviewed-on: https://review.typo3.org/28965
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer
[TASK] Improve code quality

Change-Id: I43c07ad3e29a339686d66bda4f0ccaf782fc49e9
Reviewed-on: https://review.typo3.org/28966
Reviewed-by: Georg Ringer
Tested-by: Georg Ringer