Enable the Device Feed to describe temporary traffic signals

[j-d-b]

This PR resolves #230.

Currently, in WZDx v4.0, a connected temporary traffic signal device can be represented using a LocationMarker, however, no information can be provided about it.

This PR creates a new TrafficSignal field device that allows representing a traffic signal in a WZDx DeviceFeed as its own object with specific properties that apply to it.

The follow changes are proposed:

• Deprecate the temporary-traffic-signal value on the MarkedLocationType enumerated type.
• Add TrafficSignal object with core_details and mode properties.
• Add TrafficSignalMode enumerated type, used by the TrafficSignal mode property.
• Add "See object" references to FieldDeviceType value descriptions.

[RHolt-RIDOT]

thanks for suggesting / advancing this. Note, current MUTCD defines a Flashing Beacon as a type of Traffic Signal, so suggest checking/confirming that there won't be any issues or confusion with the terminology being used (either term above).