Plot a set of 3D points in space and select a subset of them
interactively, using an rgl window

`select_points(points, clear_plot_on_exit = FALSE)`

## Arguments

- points
a matrix of 3D points to plot (or an object for which
`xyzmatrix`

can extract 3D points).

- clear_plot_on_exit
Whether to remove points from the rgl scene when
selection has been completed.

## Value

A matrix describing selected 3D points

## Examples

```
if (FALSE) {
# Select points from 3 olfactory projection neurons
selected_points = select_points(Cell07PNs[1:3])
}
```