Make the Python package build to independent release/project

[avramidis]

Is your feature request related to a problem? Please describe.
The way the project is set up now is around the Python package build. Even thought this is a good example to build code that uses SODECL it gives the impression that SODECL is a Python package.

Describe the solution you'd like
Write better description of SODECL Python package. Maybe consider creating different releases for only the header files and another one for the Python package. However, this could increase confusion.