Cleanup tests, add test for 2110, format all documents with black

Makefile

src/icartt/__init__.py

src/icartt/dataset.py

tests/_utils.py

tests/read_and_write.py

tests/test_1001.py

tests/test_2110.py

tests/test_bulkIO.py

tests/usage_examples/create_ffi2110.py

tests/usage_examples/read_ffi1001.py

tests/usage_examples/read_ffi2110.py