Improve style of incident type toggle button hover/active
Draw incidents-in-progress until current time, not end of chart
Improve styling of the incident listing

* use a combination of background-color and lighter color for headings
  to dim out minor incident rows, versus opacity (which made text
  difficult to read and is more expensive to paint)
* Remove a little bit of extraneous padding at the top
* Tighten up vpadding on each row from 1rem -> 0.75rem