added package description file

only add_subdirectory(examples) if `examples` exists. This then
allows us to not include `examples` in the pypi source distribution.

Update package.py.

Remove manifest in package.py.

use more of the cmake variables in python/setup.py.in

Add additional meta data to dune.module.

[bug fix] remove debug output

added files generated when calling python setup.py sdist to git ignore list

make it possible to use setup.py without having an installed dune-common python package. This requires having the PYTHONPATH set as it is now done in dune-common/bin/dunepackaging.py

Replace ProjectAuthorEmail by ProjectMaintainerEmail.

Set minimal versions to 2.8.0.dev0 in pyproject.toml.

Update cmake version.

[python] remove dune packages from 'install_requires' in setup.py.in

each with own script