Preliminary Gameplay Prototype (step 4)

A fourth iteration of the basic eater gameplay prototype. Like its predecessors, it is to be implemented in all the candidate frameworks listed here: https://blueprints.launchpad.net/eaterworld/+spec/client-framework-choice . Depending on the work's complexity at this point; we may start culling candidates.

New Elements
• Circular larger-than-screen playfield. Wiewport scrolls slong with player motion.
• Viewport (i.e. playfield area displayed on screen) depends on player eater's size.
• If needed at this point: liminality threshold (things too big or too small disappear from sight and do not interact with the player)

While not indispensable at this point, we should start steering the code into a structure that will allow an easier client/server separation (needed later to allow online play).