Added motorcyclist as a party to filter by
Abstracted the method to find the involvement of any mode
Added taxi and truck as parties
Made the injury filter by the **worst** injury, not just whether a particular type of injury is witnessed. Made no sense to show a fatal crash with the no injury filter.
Added speed as a filter factor
Abstracted the method to get a factor/role Boolean (for filtering)
Removed deprecated dependency on folium