extract version into separate module

[asmodehn]

extracting version into separate module to allow retrieving version from setup.py without requiring all dependencies.

[asmodehn]

Currently running setup.py to build a release, install the package or anything else, requires having all opengeode dependencies already installed in the environment. This prevent using the dependency mechanism in setup.py and have them automatically installed via pip, as installing a usual package would do. Meaning we also cannot test that the package will install the required dependencies when someone will install it.

Having the version readable like in this PR allows someone to :

• clone the repo
• create the virtual environment
• install the package with pip install -e . and all runtime dependency are automatically installed via pip (a subset of all dependencies used during development - the ones in requirements.txt) And when the package will be released, anyone installing it will also retrieve and install its runtime dependencies transitively.

Ref: https://packaging.python.org/en/latest/guides/single-sourcing-package-version/?highlight=__version__ Current solution is point 6. (and I am talking about the warning there) Proposed solution here is point 3. to not have that problem.