Added basic circular wall to simulator.
Altered behaviour to follow walls when colliding
Altered graphics code to allow for arbriatary arena position. (This makes life easier for later calculating PIs.)
Output altered to include larva position
Refactored to changed where simulation settings are set. Everything should now be set in SimRunner. This entailed some redesign of Simulation and Larva - in particular, Larva object can now acess the simulation in which it is running.
Various cleanup.