Variable tick time simulation for cyphesis

Cyphesis currently uses fixed ticket intervals to run the simulation of large numbers of mostly biological entities in the world. In order to ensure the load can be managed it needs to be possible to vary the tick period according to how loaded the server is, and reduce the computational cost of the simulation as much as possible. Once the tick interval is fully variable it should be possible to suspend the simulation entirely when there are no observers, and restart as soon as the entity is observed once more.