[TASK] Optimize ApplicationContext code

Use strpos() and explicit in_array() as well as fixing comments
and class inclusions.

Resolves: #77386
Releases: master
Change-Id: If72ed72dd14531cccad8be80070ce1c622cf9209
Reviewed-on: https://review.typo3.org/49350


Tested-by: Bamboo TYPO3com <info@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>