add version.py and __version__ to the package

[codingpaula]

Motivation

To evaluate the version of the devkit package we are using a __version__ property for the package.

Implementation

The version.py determines the correct version using importlib.

Progress

• I chose a meaningful title that completes the sentence: "If applied, this PR will..."
• I chose meaningful labels (if GitHub allows me to so).
• I documented breaking changes and set the 'breaking change' label if needed
• The implementation is complete.
• Tests with a real hardware have been successful (or are not necessary).
• Pytests have been added (or are not necessary).
• Documentation has been added (or is not necessary).