Show all member names on hover

[jdcc]

Becca would like the ability to show all members of a cluster when hovering over a cluster.

This could happen when hovering over the cluster itself, which is intuitive but might interfere with other dot interactions, or it could happen when hovering over the cluster label.

To make this more abstract, given that not every survey will have a name field and we won't know what field that is, we'll need to add a setting that allows the editor to designate the question for which the answers should pop up when hovering over a cluster.