Update .gitlab-ci.yml for gitleaks

See merge request !1

* Generating a timetable for yard duty/supervision. daVinci is providing it directly, for untis we must guess based on the pupils timetable.
* Read out the standins from supervision.txt for untis and generate the necessary entries.
* **Functional limitation**: the regular plan for yard duty is not interpreted yet (should we?)

Offer parser feature to parse only first found file.
This is required whenever a parser needs to parse several files (e.g. a file teacher.txt, lesson.txt,...).

Determine parser automatically depending on enabled parsers and supported extensions. Note, that only one parser of a file extension should be enabled.