INFO: bqplot marker properties

This documents the properties that markers can have in bqplot. See [this link](https://bqplot.github.io/bqplot/api/marks/#bqplot.marks.Scatter) for a more complete list of scatter properties; some of the highlights are below.

| Property | Default | Description |
| ------- | ------ | ---------- |
| color | 'steelblue' | Color of the marker|
| opacity | value of `default_opacity` | 1d array of marker opacities |
| size | RELATIVE size of markers | 1d array of sizes. The largest marker is set to a size, in pixels, of `default_size` and smaller markers are scaled from there. |
| default_size | 64 | Size, in pixels, of the default marker. If `size` is set, then `default_size` is the size of the *largest* marker |
| skewness | value of `default_skew` | 1d array of skews |
| rotation | 0 | 1D array of orientations of each marker |
| icon | ? | icon for the mark |
| marker | `circle` | Shape of the marker |
| colors | 'steelblue' | list of colors of the markers (how is this different thatn `color` above?) |
| fill | True | Whether to fill the markers |
| stroke | None | stroke color of the marker |
| stroke_width | 1.5 | stroke width of the marker |
| default_skew | 0.5 | Skew of the marker |
| names | None | labels for the points on the chart|
| display_names | True | Controls whether names are displayed |

The issue links to bqplot's Scatter API page and lists marker properties in its body; start by comparing that reference with the table, especially the difference between color and colors. Done means the marker-property documentation is accurate, complete, and explains any unresolved defaults or distinctions.

Written by the indexing model from the issue text.