Add function to get CADET version

[hannahlanzrath]

It would be beneficial to add a function to get the version of the currently used CADET installation (before a simulation has run). That can be achieved by reading out the cadet-process metadata, similar to how it's done in CADET-Process.

[schmoelder]

Hey, didn't we already include this?

[hannahlanzrath]

Still has to be migrated from CADET-Process to CADET-Python.

[schmoelder]

Apparently the functionality was already present in the runners and i only needed to wrap it in a property. More info in #55.