Create sub and super configuration wrappers.

Create wrapper configurations to represent live views of a subtree or parent tree of an existing configuration.

A subconfiguration will act like a subset of keys, but the subconfiguration will act as if the prefix of the subtree were removed. For example if a configuration contains foo.bar.example, in the subconfiguration for prefix foo.bar the same key would be accessible as example, and no keys outside that keyspace would be accessible.

A superconfiguration will act like a superset of keys, but the superonfiguration will act as a prefix were added to all keys. For example if a configuration contains example, in the superonfiguration for prefix foo.bar the same key would be accessible as foo.bar.example.