Support other data source types for chart builder

[nosnickid]

Our chart builder addon currently only lets you load data from "File" plone content, by expecting you to upload a tidy CSV and then using the @download route to directly access the content.

This could be extended to support the EEA data "@connector-data" routes as a proof of concept for accessing other data types provided by plone.

[JasonHowell]

@anojperera to review.

[nosnickid]

Prereqs

• "EEA data connector" Plone extension is enabled

Acceptance

• Create a 'Discodata connector' query
• Use the default query, and add order by country, av_p_size to it
• Save and view the query; you should see a table with data
• Create a new Document in volto
• Create a chart builder block
• [ ] Using the "CSV Data" selector at the top of the chart builder edit side panel, you can navigate to select your Discodata connector
• [ ] Category Axis / Measurement / Dimension offer you the columns from the result
• Select Category Axis = AV_P_SIZE, Measure = HA_05, Dimension = Country
• [ ] 'Data Series' gains a "+" button and you can add per-country data series to the chart
• [ ] The chart shows the data ultimately received from the discodata connector