Preliminary Gameplay Prototype (step 5)

A fifth iteration of the basic eater gameplay prototype. To be implemented in all the remaining candidate frameworks from https://blueprints.launchpad.net/eaterworld/+spec/client-framework-choice that haven't been culled after the previous iteration. After this iteration we should reduce the candidate list to two or three finalists.

New elements
• If not already implemented: liminality threshold (see https://blueprints.launchpad.net/eaterworld/+spec/gameplay-prototype-4)
• Swallowing: an eater can become contained completely inside another eater's body. Conditions for this are yet to be resolved.
• "Vampiric Swallow": an eater can swallow some (or all) of the eaters inside another eater's body when the former bites the latter.
• Swallowed entity is partially digested (i.e. part of its mass is absorbed by the swallower) if above liminality threshold.

Alternative to test
• Latching: holding the bite button would cause the biter head to latch onto the bitten body and be pulled and towed around with it.