Split scatter module

[etpinard]

@mdtusz @cldougl @alexcjohnson

[etpinard]

By doing so, we get rid of two circular dependencies:

• Scatter <-> Drawing and
• Scatter <-> ErrorBars

[etpinard]

slightly abusive, but it's the only way to clear us of circular dependencies while keeping things 🌴

[etpinard]

Another thing to note, with this PR, no src file requires the full Scatter module (i.e. no files has traces/scatter/index directly or Plotly.Scatter). So, 'scatter' does not need to be part of the 'core' module for things to work.

That is, we can remove these lines in src/plotly.js.

That said, should we make the pro users register the Scatter? I'd vote for yes. Its plot step is quite big.

[mdtusz]

+1 for making pro users register all/any traces.

[mdtusz]

I'd say that in Plotly.plot, we should just throw an error if no traces have been registered.

[mdtusz]

This looks good to go though 💃

[etpinard]

@mdtusz

I'd say that in Plotly.plot, we should just throw an error if no traces have been registered.

agreed. 👍