Milestone ActualityEpic

"As a player, I want a world to exist which I can connect to, so that I can play in it."

This will involve creating the Area class and its superclasses (Locus and Entity), the Character class and its parent ComposedObject, and the Spirit.

• Locus should have basic Containment — adding and removing contents, container callback, containment predicates, etc.
• The Area and Entity classes can be mostly empty, as most of the functionality for this epic will be provided by Locus.
• ComposedObject needs an inner 'Constituent' mixin that expresses the API ComposedObject requires of the objects that compose it, and should provide a generator for setting up the constituents in derived classes.
• AnimatedObject should derive from ComposedObject and provide an association to a Spirit.
• Spirit will need hooks for input and output (#onInputReady and #onOutput), and be able to associate it self with an AnimatedObject.