Type should be validated instead of defaulting to scatter

[tbitai]

Currently if a plot type is invalid, it will default to 'scatter' instead of throwing an error. This is quite misleading if one uses a partial bundle and doesn't realize that the type they want to use is not in that partial.

Example: https://jsfiddle.net/tbitai/uahw2ycd/ This will be incorrectly rendered as a scatter plot, since the 'surface' type is not contained in the basic bundle.

[etpinard]

We don't throw errors on bad attribute values anywhere in our code. So this would be a first. You may have a point that defaulting to scatter in partial or custom bundles isn't ideal. I'd recommend using Plotly.validate (see https://jsfiddle.net/uahw2ycd/28/ for an example) before calling newPlot.

Related #1741

[tbitai]

Thank you! Closing this, since #1741 addresses the same issue more generally.