Final feature updates

[mwbernard]

This PR takes care of three final client requests:

1. it moves the scenario toggle above the map-mode buttons in the sidebar

2. it adds a small arrow to the crop group metric toggle

3. it adds a tooltip to the crop group stacked bar chart that only appears when you hover the stacked bar. the text is just which crop you're hovering

[mwbernard]

@kelsey-taylor good catch, I had a margin on the chart itself that was pushing it outside its spacing bounds. Switch margin to padding and should be all good now!

[kelsey-taylor]

looks good — feel free to merge!