* Registry no longer exists. Its functionality has been split between utilities and the Command class.
* Services are now passed a root command rather than a registry object, similar to the previous idea of the PrefixedRegistry, but much cleaner.
* All of the special handling required for Fusion to deal with multiple registries has been wiped out, even though I just spent hours rewriting it earlier. This is much better.
This is to prevent surprises with command keys not matching their names, particularly if a command is aliased multiple times. Renames now require re-registration.
