Merge branch 'cleanup_BackendModule' into 'master'

Classes/Preview/PreviewService.php

Resources/Private/Backend/Partials/Filter.html

Resources/Private/Backend/Partials/Pagination.html

...urces/Private/Backend/Partials/PluginDataTableHeader.html

Resources/Private/Backend/Partials/SelectRoot.html

Resources/Private/Backend/Templates/Index.html

Resources/Private/Backend/Templates/JobApplication.html

Resources/Private/Backend/Templates/JobTeaser.html

Resources/Private/Backend/Templates/Joblist.html

...rces/Private/Templates/AA_TODO-WAS_IST_DAS-BACKEND-ORDNER

Resources/Public/JavaScript/Backend/SgJobs.js

Resources/Public/StyleSheets/pluginpreview.css