New Executor Backend for Parallelism with Joblib and Dask

🚀 Features

• Add Executor class and CLI arguments for parallelism @bouthilx (#608)
• Orion python api in parallel @donglinjy (#601)

🏗 Enhancements

• Add has_suggested/observed, new test-suite and re-implementation of ASHA @bouthilx (#604)
• Refactor hunt command to reuse ExperimentClient.workon @bouthilx (#605)

🐛 Bug Fixes

• Test different type of categorical dims @bouthilx (#609)
• Add has_suggested/observed, new test-suite and re-implementation of ASHA @bouthilx (#604)

📜 Documentation

• Documentation for the visualizations @bouthilx (#557)
• Add has_suggested/observed, new test-suite and re-implementation of ASHA @bouthilx (#604)
• Add presentations section in doc @bouthilx (#597)