Using a named data source in Vega-Lite

This uses data.name in the chart spec, and vegaEmbed with Vega-View to load data at runtime and update the chart.

This really doesn't want null values in encoding.y.title and encoding.x.title - so ensuring those are populated makes this work. "title": " " works where "title": null does not, FYI.

Additionally, this creates a calculated field within vega-Lite, using parseFloat to add columns to create a new one.