Memory leak

[mauicv]

The lawInstance exports are IIFE and returns an object that seems to persist across multiple instances of the engine environment created in one session. This may be causing a memory leak. If using a single engine instance it's not a problem but if instances are saved then the laws hold references to each environment causing both memory pollution and extra engine cycles. The hacky fix is just to reassign the relevant law instances at engine creation to new ones.