[CLEANUP] Code Cleanup EXT:aboutmodules

Refactor the code to go green in PHPStorm.
Main tasks:
* Initialize variables
* Centralize objects in $GLOBALS

Resolves: #62689
Releases: master
Change-Id: Ia48365341da93d6f3bc86af53840a8bfeb45feb6
Reviewed-on: http://review.typo3.org/33782
Reviewed-by: Stefan Froemken <froemken@gmail.com>
Tested-by: Stefan Froemken <froemken@gmail.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>