Optimize Helptablemanager.php

[TamaroWalter]

The Helptablemanager does to things:

• fill in Datatables from lsf_unification manually (does the same thing as the cron-job)
• Create mappings of categories. This is essential to create courses as a mapping of the lsf categories to the moodle categories needs to be done before a teacher wants to create a course (or else the teacher is stuck a the request_form.php for not choosing a valid new category for the course)

Optimize this page with a beautiful template and good functionality is a good way to start the redesign of the plugin!

[TamaroWalter]

This Issue is tackled in the redesign/update_helptable branch. A PR will be there when the branch is in a review-ready state.