Merge branch 'f-converter-submodule' into 'dev'

CHANGELOG.md

src/caoscrawler/__init__.py

src/caoscrawler/conv_impl/__init__.py

src/caoscrawler/converters/__init__.py

src/caoscrawler/converters/converters.py

src/caoscrawler/converters/hdf5_converter.py

src/caoscrawler/converters/spss.py

src/caoscrawler/converters/xml_converter.py

src/caoscrawler/default_converters.yml

src/doc/converters/cfood_definition.rst

src/doc/converters/custom_converters.rst

src/doc/converters/further_converters.rst

src/doc/converters/standard_converters.rst

src/doc/how-to-upgrade.md

unittests/h5_cfood.yml

unittests/test_converters.py

unittests/test_h5_converter.py

unittests/test_xml_converter.py