generates a random world, sets terrain and runs agents in it
     TODO - need to change pieces in multiple places (see worlds.py, cls_grid, world_generator)
     (takes about 5 minutes to make 500x400 grid with 8% blockages)

def main():
    """
    generates a random world, sets terrain and runs agents in it
     TODO - need to change pieces in multiple places (see worlds.py, cls_grid, world_generator)
     (takes about 5 minutes to make 500x400 grid with 8% blockages)
    """
    width       =  20   # grid width 
    height      =  10   # grid height
    iterations  =  20   # how many simulations to run
    num_agents  =   6   # number of agents to enter the world
    
    w = build_world(height, width)
    print(w)
    a = create_random_agents(w, num_agents)
    sim = my_world.WorldSimulation(w, a, 1)
    sim.run(iterations, 'Y', log_folder + os.sep + 'agt_run')
    sim.world.grd.save('test_world_traversed.txt')