Add add_*() functions for each trace type and provide error checking

[cpsievert]

• For example, add_scatter()/add_bar()/etc. These would essentially be thin wrappers around add_trace() with the proper type.
  • Throw errors for when required properties are missing. For example, add_scatter3d() requires x/y/z.
  • Throw errors for when a property is of the wrong type. See, for example, plotly heatmap doesn't take a dataframe #329.

@timelyportfolio this would maybe be a good exercise if you're up for it?

[timelyportfolio]

I really like this idea. I'm working on the toImage issue on the JS side. Ok if I pick it up after I complete that?

[cpsievert]

Sure thing. I forgot to mention that we should try to provide the same error checking in plot_ly()

[cpsievert]

BTW, it'd be nice to have a dynamic list of acceptable arguments to check against for each trace type. Ages ago, I created this script to scrape the reference for arguments, but it should really be generated from plotly.js, and updated whenever we upgrade the plotly.js bundle