Scherbelberg

- FEATURE: Moved all cluster configuration files, scripts and keys into hidden folder named equivalent to the cluster prefix, both local and remote.
- FEATURE: New CLI and API for accessing the catalog of server types, their specifications, prices and data center locations.
- FIX: Setting debug environment variable `SCHERBELBERG_DEBUG` to `1` also automatically lowers the log level to `DEBUG` (`10`) if *scherbelberg* is used via the CLI.
- FIX: Added missing logging during cluster destruction.

- FEATURE: Dask scheduler and worker processes run as systemd services, allowing them to be restarted and the nodes to be rebooted, see 1.
- FEATURE: Raise proper exceptions when trying to connect to a broken or not existing cluster.
- FEATURE: CLI shows proper messages when trying to connect to a broken or not existing cluster.
- FEATURE: Workers and scheduler run the same major & minor version of Python as the client does, see 2.
- FEATURE: `scherbelberg ssh` can directly run commands on the remote host if passed as an optional string on the command line.
- FEATURE: Added `scherbelberg scp` command to complement the already existing API.
- FEATURE: Added log level option, `-l` or `--log_level`, to all CLI commands, see 5.
- FEATURE: Run-time type checks become an optional debugging feature and can be activated via an environment variable, i.e. `SCHERBELBERG_DEBUG=1`.
- FIX: Remove remaining dependencies to Python wheels.
- FIX: Python language server dependency set to up-to-date package.
- FIX: Inconsistent CLI output behavior depending on platform.
- FIX: All error messages go to stderr.

- FIX: Remove old and empty `scripts` parameter from `setup.py`.

- FIX: Encoding of `README.md` explicitly set to UTF-8. Installation would fail on Windows otherwise.

- Include docs into source distribution.

- Initial release.