Redistribution of equity neighborhood bins to match MSA bins

[wklumpen]

For the Equity Neighborhood percentile-based legends, lock the categories & colors to the MSA categories, rather than distributions within the set of equity neighborhoods themselves. So that an Equity neighborhood that’s in the top 20% of the MSA but the 40-60th percentile of other equity neighborhoods appears in the top 20% category when MSA is selected or when equity neighborhood region is selected.

[wklumpen]

Unfortunately the way the data request is set up to the database, I only grab the data I need (urban core, msa, etc). This means that I don't have a "reference" set of bins to use for the MSA category.

Updating it to do this would be a fairly major change and might introduce more performance problems. So keeping it on the backburner for now.

[mlbtc]

Since the goal is to show how equity neighborhoods fare on these metrics, compared to the rest of the region, another option might be to add the outline of the equity neighborhoods as an overlay on any of the regional subsets.

[wklumpen]

This is addressed in #124 by creating fixed bins for the entire region and keeping those values fixed despite the geographic block group filter.

If there are any additional changes still needed for equity neighbourhoods specifically, feel free to re-open.