ML Notebook cleanup

[beccamc]

• Ensure Model Builder references are removed.
• Link to appropriate reference sections
• Spell check
• Content
• Remove "Unknown => " from the pipeline. Rename "Pipeline" to "Trainer". Add parameters column.

[wldevries]

Might be nice to replace WebClient with HttpClient in 02-Data Preparation and Feature Engineering.ipynb. It's flagged as a warning.