First commit of "dev" branch. Ensemble simulations.

Now, in addition to the cumulative simulations, we can perform an ensemble of simulations where for each one, the score is only calculated at the end of the run, so the score isn't accumulated throughout the simulation.
Minor changes to dev branch
Minor change to dev branch
Displacement statistics

A few functions are added so that the displacement of each agent from its initial position can be measured.

This is useful  for studying the distribution of the distances travelled.
Generalized origin defined

Instead of just one point, now "origin" means all points in a square
neighborhood of the origin whose size can be defined. Score computation
is accordingly modified.
MAJOR BUG CAUGHT

I discovered a major bug in updateScore(). I wasn't linking all agents
in the generalized "origin". Rather, I was still linking each such agent
only with other who were at the exact same point as the agent. I have
corrected that.

Simulations show that the degree distribution due to the cumulative
model is still exponential.