Add placeholder #start method.
Interface does not implement it’s own event loop.
Interfaces rethink;

- When defining interfaces we instantiate them immediately for access.
- Demote .default method to private.
- We can now access interfaces through .defined; creating them if necessary.
- Don’t return the hash of interfaces, this is leaking implementation to the rest of the system, inviting me to manually tamper with interfaces. Instead, use Interfaces module.
- Add methods for .input and .output; these will delegate to defined interface classes.
Delegate methods to Interface. Serves as documentation.
Add basic, manually tested event loop.