Implement fall-back template-set for robust PDF export

[scaphilo]

Context:
Currently the user has to define all templates from scratch and there is no fallback solution. The user is asked to properly fill out the templates sets. This often leads to issues (especially on the demonstration and during first contact with the tool) . As this affects mainly new users which want to see how to work it is very annoying

Improvement
Within this issue, it is planned to implement a fallback template-set. When the user has not selected a template set, the user is equipped with the default template set to avoid crashes during pdf export