Add "event_type" field to road event entity to accomodate detours (and more)

[DeraldDudley]

Include Detour Information for a Road Event

Reference Issue #82

• This pull requests inserts a property / member called "event_type" onto the road_event entity.
• The "event_type" property classifies the road_event as either a "work zone" or a "detour"

GeoJSON detour example: https://gist.github.com/DeraldDudley/d5a1d9e5a6dd3add5f7a1b9d007a5c2c

1. Updated road_events table to add a single new field.

Field Name	Data Type	Description	Conformance	Notes
event_type	Enumeration; Text	Indicates the type of road event	Required	Enumeration: “work-zone”, “detour”

2. Added a new enumerated type

Event Type Enumeration

Type	Description
work-zone	An area of a trafficway with highway construction, maintenance, or utility-work activities. A work zone is typically marked by signs, channeling devices, barriers, pavement markings, and/or work vehicles. It extends from the first warning sign or flashing lights on a vehicle to the "End of Road Work" sign or the last traffic control device. A work zone may be for short or long durations and may include stationary or moving activities. Inclusions: Long-term stationary highway construction such as building a new bridge, adding travel lanes to the roadway,1 and extending an existing trafficway.2 Mobile highway maintenance such as striping the roadway, median, and roadside grass mowing/landscaping, and pothole repair. Short-term stationary utility work such as repairing electric, gas, or water lines within the trafficway. Exclusions: Private construction, maintenance, or utility work outside the trafficway. 1 The AASHTO term equivalent to roadway is traveled way. 2 The AASHTO term equivalent to trafficway is highway, street, or road.   Source: https://www.fhwa.dot.gov/publications/publicroads/99mayjun/workzone.cfm
detour	A temporary rerouting of road users onto an existing trafficway to avoid a work zone or other impedance.   Source: https://mutcd.fhwa.dot.gov/htm/2009/part6/part6c.htm

[j-d-b]

~There are a few issues with the specific implementation of this PR. Mainly, in road_events.md the entire table is rewritten and loses its formatting (bold pieces, code, hyperlinks, etc) even though just one property is added. Additionally, the examples and schema need to be updated to reflect the addition of the type field and corresponding enumeration.~

Edit: all resolved; see below.

[j-d-b]

Updated the examples and schema.

Edit: re-implemented the type field addition to fix the table formatting and diff as well

[j-d-b]

@DeraldDudley what do you think about naming the new field event_type rather than just type. Though largely just style, I was thinking it felt a bit more clear, and is consistent with the event_status property already on the road event.

[j-d-b]

Updated field from type to event_type and the enum from "road event type" to "event type" for consistency with event_status field and "event status" enum.

[DeraldDudley]

@DeraldDudley what do you think about naming the new field event_type rather than just type. Though largely just style, I was thinking it felt a bit more clear, and is consistent with the event_status property already on the road event.

I agree. No objections here.