ENH: add sav converter

.docker/Dockerfile

.gitlab-ci.yml

setup.cfg

src/caoscrawler/__init__.py

src/caoscrawler/conv_impl/__init__.py

src/caoscrawler/conv_impl/sav.py

src/caoscrawler/converters.py

src/caoscrawler/version.py

src/doc/converters.rst

unittests/test_converters.py

unittests/test_sav_converter.py

unittests/test_tables/spss/CITATION.cff

unittests/test_tables/spss/LICENSE

unittests/test_tables/spss/sample.sav

unittests/test_tables/spss/sample_large.sav