Event Frame UI improvements within the Treemap

[jrsconfitto]

• Hovering over the EF gives it a border
• Better text on each EF? i suggest allowing the user to select an Attribute, Name, or Start/End dates in the config screen. Is the default of the EF Name a good one? It doesn't seem to demo well ☹️

i think the following one would be a little harder:

• Clicking on an EF (say to show its attributes in a table), puts it into a visibly "selected" state