[TASK] Upgrade ext:scheduler to a modern file structure

* Move images to Resources/Public/Images/
* Move language files to Resources/Private/Language/
* Migrate ExtJs to jQuery
* Move module template to Resources/Private/Template/
* Add strict comparison were possible

Resolves: #60630
Releases: 6.3
Change-Id: I7bae64263268562b158dccf9b9c8fa6d6726fe52
Reviewed-on: http://review.typo3.org/31875
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Markus Klein <klein.t3@reelworx.at>
Tested-by: Markus Klein <klein.t3@reelworx.at>