Miki/people api extension

@raypereda @DavidHuie 

This is the documentation update for the [People API extension](https://github.com/3dna/nbuild/pull/1015).

* document person and abbreviated person resources
* add address3 field to the address resource and sample payloads
* update payload samples for the people api endpoints and the people webhooks
* update instructions about changing the webhook versions