Migrate logout-scripts to controllers

i3x PSR012

Office Webviewer doesn't like arrow functions and throws a syntax error

Instruct embedded IE to behave like the most modern browser they can

From the docs:
Include es5-shim especially if your browser doesn't support ECMAScript 5 - but every JS engine requires the es5-shim to correct broken implementations, so it's strongly recommended to always include it. Additionally, es5-shim should be loaded before es6-shim.

Upgrade Gettext

This reverts commit dabe7e47.

Use Symfony/filesystem