Documentation reorg: Development docs
Created by: christinaforney
Reference: https://docs.google.com/document/d/1bOGK1s6KeIp8CVbYvb3xOsv6k8_XxQQRLOZVcAGbORc/edit#
This is the first of several PRs, but broke down into steps to make the whole thing easier to understand.
Organized the developer documentation into 3 categories (see above reference for where this structure came from):
- Getting started
- How-to guides
- Background information