Restructure modules, track authentication capability in phantom type
Provide Hashable instances for ServiceKey + IncidentKey
Remove Hashable instances again, add more useful Ord instances
Fix issues:

* unauthenticated requests don't use the subdomain, so don't carry in env
* otoh, let API impls pass a different host.
* in fact, let them create a base Request
* http-client doesn't change the port when 'secure', so set to 443
* event submission response is an object
Add "Services API" + substantial interface rework
Un-export datatype (was exported for debugging purposes only)
Add support for the "Maintenance Windows API"