Rework route service responsibilities

[ErisDS]

refs #9192, refs #9178

After trying to progress with current implementation, it became clear that the route service can't control the boot sequence, because then we end up with circular dependencies between the route service and the channel service.

The route service now exposes:

• a siteRouter
• a way for apps to register routes.
• ParentRouter base class for other modules to use
• the registry

...

• moved the default route setup back to site/routes.js 🙈
• moved the parent channel router back to the channel service (this makes way more sense imo)
• this structure prevents circular dependencies
• split the registry out into it's own thing
• fixed-up various bits of tests and comments
• DEBUG will print a list of routes 🎉