[CLEANUP] Initialize variables and fix some PHPDocs

* initialize variables before they are used
* do not use FQ namespaces if not required
* fix PHPDocs
* add missing return statements

Resolves: #67797
Releases: master
Change-Id: I581ae9ac8c0a277a415d9ba69812305951a86464
Reviewed-on: http://review.typo3.org/40705


Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Stephan Großberndt <stephan@grossberndt.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>