Updated \studeidesstatt to meet changed requirements of PVO and FPO

The 2019 "Fachprüfungsordnung" for Computer Science (and the subsequent 2021 version) requires digital submission of the bachelor and master thesis to the examination office. This changes the requirements for the "Selbstständigkeitserklärung" to include a statement that the digital and the print version are equivalent (see § 12 (6) PVO.)

This merge request is the modification I applied for my thesis to include such a statement. I do realize that there may be a need to disable this second paragraph of the assurance, but I lack the \LaTeX knowledge to implement such a feature. Also, the text I added there might not be the best possible way to word such a statement.