Developer Guide End-to-end setup instructions for Linux, Windows, and macOS (#5003)

* End-to-end setup instructions for Linux, Windows, and macOS

This covers E2E setup instructions for compiling Kubernetes locally on
Linux, Windows, and macOS workstations. There is also a substantial
rewrite of the instructions for running tests, along with relevant
links for more information.

* Clarification of a few changes to the Developer Guide

Cleared up instructions for jq and etcd in the Developer Guide.

* Developer guide: add note about shell init scripts in macOS

Author: pymander

contributors/devel/README.md

@@ -134,7 +134,6 @@ See the [kubernetes/release](https://github.com/kubernetes/release) repository f
 * **Using Go Modules to Manage Dependencies (for Kubernetes 1.14.x and earlier)** [godep.md](sig-architecture/godep.md)
   See [current documentation for working with dependencies](sig-architecture/vendor.md) for master branch development.
 
-### SIG Architecture
 * **Conformance Testing in Kubernetes** [conformance-tests.md](sig-architecture/conformance-tests.md)
 
 ### SIG API Machinery