Jackson 3.0.0 default for SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS

[cowtowncoder]

(part of #72 uber-Discussion)

As of Jackson 2.x, SerializationFeature.WRITE_DURATIONS_AS_TIMESTAMPS defaults to true for backwards-compatibility.
A suggestion has been made:

FasterXML/jackson-databind#4846

to change it to false instead, to improve JSON readability by defaulting to textual serialization over numeric timestamps which, while more efficient, are less human-readable.
We cannot make the change in Jackson 2.x, but could change it for 3.0.0.

So let's see if there is consensus on whether to make proposed change.