[TASK] Refactor EM JavaScript

* Use IIFE for faster access to jQuery and save $ use
* Make JS lint-free

Resolves: #42325
Releases: 6.0

Change-Id: Ia014de44570306ce9c5cd02c97a228205a7a2849
Reviewed-on: http://review.typo3.org/15915
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel