Bug fixes to update registered environment and ensure compatibility with AML Datasets

What's Changed

Bug fix to ensure that when existing, registered environments are retrieved, the run_config is updated accordingly. Another bug fix for pinning Ubuntu version to 18.04 since later versions are not currently compatible with Azure ML Datasets. Also adds local dataset mounting, and a helper function for downloading and aggregating the metrics across all children of a hyperdrive run.

• Locally mount datasets by @JonathanTripp in #145
• Add k-fold cross validation wrapper around HyperDrive by @mebristo in #149
• Profile methods for loading png image files by @JonathanTripp in #132
• Bug fix: update run_config with registered environment by @mebristo in #156

Full Changelog: v0.1.10...v0.1.11