rename repository and/or fix up inconsistencies between python package and cli naming ?

[foreveremain]

There's some dissonance between the name of the repository (slivka-python-client), the name of the python package the repository provides (slivka_client), and the executable added to the path on installation (slivka-client ? though

slivka-python-client/slivka_client/__main__.py

Line 13 in 07e45a4

@click.version_option("1.2", prog_name='slivka-cli')

suggests slivka-cli ?).

It would be good to have one single consistent name, and perhaps also avoid Java CamelCase if we might be able to !