Determine template name from MultiplTranslatedProperties

WIP

Do not prefix the template property for snippets.

This is another loan from the bank of technical debt, but its not too much.

__Tasks:__

- [x] test coverage
- [ ] gather feedback for my changes

__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | [yes|no => <WHY?>]
| Fixed tickets | [<WHICH?>|none]
| BC Breaks     | [description]
| Doc           | [url to commit|none]
@wachterjohannes Moved this logic from the SessionManager in another PR. Here I changed it again to always match the `base` path and then the webspace.