Add experiment tracking using mlflow

[wouterjdb]

This PR adds the possibility to run multiple flownet configuration files and do experiment tracking using mlflow.

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Contributor checklist

• [x] :tada: This PR closes #232, #233
• [x] :scroll: I have broken down my PR into the following tasks:
  • [x] Add mlflow dependency
  • [x] Add hyperopt dependency
    • [x] Expose choice between random search and optimization
  • [x] Add hyperparamter running mode in arg parse
  • [x] Parse configuration file with ranges and choices
    • [x] Initial parsing
    • [x] Add flexibility for user
  • [x] Generate mlflow experiment
    • [x] Run flownet
    • [x] Generate metrics and store in mlflow
• [x] :robot: I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR.
• [x] :book: I have considered adding a new entry in CHANGELOG.md.
• [x] :books: I have considered updating the documentation.

[wouterjdb]

Tested now with the Egg CI Model. The workflow is working using hyperopt and visualization/tracking with MLFlow:

I track however a metric of "1" at the moment. Still a todo. Let's look at this tomorrow @edubarrosTNO.

[wouterjdb]

Added metrics and parameters. Exposed hyperopt options in config.