Simulation statistics

Added several statistics about the model+controller's performance.
Now sim.Run outputs a struct that includes several statistics about the
simulation performance including: X, T, Torques, the stance foot's
position, steps taken, end result, min/max slope and convergence.

In Simulation.m, removed old commented code after re-coding it for the
new sim.

Also added additional conditions for stopping the simulation when the
robot falls, takes a very very small step or hits the ground while the
leg is still shortened.