[FEATURE] Allow PSR-7 dispatching for Backend modules

The newly introduced simple dispatcher handles the distribution
of all "traditional" modules through a new option called "routeTarget" when registering a module.

All existing core modules are moved to this new syntax, all left-over
index.php files within Modules/ directories are removed.

Resolves: #69918
Releases: master
Change-Id: I6200a5e0309454fd981c9f1fa277d948974a1fac
Reviewed-on: http://review.typo3.org/43375


Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>