Layers tray enhancement

[mbwatson]

now that we have grouped layers into model runs, the user experience related to layer ordering, editing, and general browsing has grown cumbersome. namely, the experience is hindered by artifacts leftover from the previous ungrouped layers tray.

we discussed consolidating the layer buttons to simple reorderable toggle switches, as pictured in the sketch below.

notes:

• this is merely a first draft of this idea
• name change "layers" to "model runs"
• we want to retain the metadata browsing capabilities in some capacity.
• a counter badge has been included on the layers tray button
• ignore the mismatched dates