Cowait

- Kill tasks by name 198
- Network refactoring 189
- Message timestamps
- Added tests for websockets
- CLI reorganization 204
- Improved nesting of configuration files 204
- Engine refactoring
- Extracted `DockerProvider` and `KubernetesProvider` to separate packages
- Resource monitoring & Stats API 171
- Support for docker build arguments 208
- Migrated project to use Poetry for dependency management 211
- Dotenv path fix 216
- Fix problem when logging task names containing dashes 215
- Tuple serialization 214
- Reorganize test files 220
- CLI tools changed to take key-value options on `-i key="value"` format, similar to Docker 221

Additional bug-fix for issue running docker on Mac. Fix was first introduced in 0.3.4

Small tweaks and stability fixes.

- Deserialization of TaskInstances (sometimes?) caused problems when monitoring child tasks (167)
- Updated Spark to 3.0.0 (169)
- Added an `--image` option to `cowait notebook`, allowing it to use other remote images, such as `cowait/spark` (169)
- Properly encode gzipped environment variables (170)
- Fixed a bug in `cowait run` (see 163)