Add a chart for injury type
Make injury styling code a lot more general
Work harder to combine collisions in the intersection

Try to create intersection names in alphabetical order, so that
it's more likely that they will combine.
Add colored markers to the popup
Allow toggling disabled/enabled display on chart elements
Prepare for filtering

Shuffle categories into collections of data holding the names of each
category, counts, and categories filtered out.
Allow filtering by year and collision type

This is pretty early and still needs quite a bit of cleanup.