Line/scatter/area plot editor

[rreusser]

Working on getting this merged so that it can be used. I don't think there were breaking changes beyond needing to hook up both the initialization and update events to the plot. That's done in the example code here.

<Plot
  ...
  onUpdate={this.hub.handlePlotUpdate}
  onInitialized={this.hub.handlePlotInitialized}
/>

If you're using the hub from the example repo that hooks up all the pieces, that will also need to be updated. I think this hub should get moved into an export of the editor so that it can be imported seamlessly, but I haven't yet done that. At any rate, that should be an easy migration.

Usage of the plotly.js-react component has also changed just slightly. Specifically:

• plotly.js-react has been renamed to react-plotly.js
• I'll be merging Initial version react-plotly.js#6 shortly that solidifies the API and applies a number of minor decisions so that we can minimize any more big changes moving forward (like the name change, for one)

Other than that, I'm going to go over this a bit more and make sure everything can be expected to work out of the box. Once that's done, I'll merge this and notify that it's ready to go. The plan is to:

• ensure the basic features are hooked up correctly
• update documentation
• write down a few notes for upgrading

cc @ereplogle @alteryx-grose @alteryx-sezell @alteryx-smann @alteryx-vsmith @alexcjohnson @jackparmer

[rreusser]

Remaining issues:

• area charts, which depend upon the color selector
• trace deletion