Adds variable quadrant sizing

[colinhanrahan]

• New config setting: "environmentQuadrantSizeFactor" between 0 and 1.
• The default is 1, which means the quadrants agents start in each take up exactly one quarter of the environment.
• The combat examples from the book use 20x20 quadrants = a quadrant size factor of 0.8, so their configs have been modified to account for this.
• findActiveQuadrants() was wasting runtime being called every timestep, so it is now only called once at the beginning of the simulation.
• The list returned by findActiveQuadrants() is now a list of lists with each sublist being a quadrant. This will be very useful for adding specific tribes to quadrants, which can be added after this PR goes through.

[nkremerh]

Changing the findActiveQuadrants behavior does not have an impact on examples that have the agent replacement rule enabled, does it?

[colinhanrahan]

Agent replacements spawn in whatever quadrants you enable as active. So if you only use quadrants 2 and 4 for the starting agents, the replacements will also only spawn in 2 and 4. I'm pretty sure this is the intended behavior.