* config: add environment variable macros
Add support for ${env.VAR_NAME} syntax to pull values from system
environment variables during config loading.
- env macros processed before regular macros (allows macros to reference env vars)
- works in cmd, cmdStop, proxy, checkEndpoint, filters.stripParams, metadata
- returns error if env var is not set
- add comprehensive tests
fixes#462
* docs: add env macro example to config.example.yaml
Benson Wong
124007cc98