MLOps with Azure ML

Fix training/scoring conda deps (#262)

Azure deprecated their top level meta-package which led to a deprecation error. We don't actually need this top level package.

I took the opportunity to clean up the conda deps using the dependency tree.

- Trimmed the package list
- Explicitly list pip to avoid conda warning
- Use azureml-defaults for WebApp dependencies
- Lock azureml-sdk and azureml-defaults versions
- Add comments for dependencies