Fixes index mismatch between cell and environment causing breaks

[colinhanrahan]

Current repo:

• Cells are indexed by (x, y) or (width, height).
• Environment is indexed by [height][width]. See line 5 of environment.py.
• Due to this mismatch, any environment size that is not square breaks.
• "North" is considered to be in the positive y direction (downwards on GUI).

This PR:

• Having to choose one of the two coordinate systems, sticking with Cell (x, y) makes more sense.
• Environment is now indexed by [width][height] (required changes to multiple files).
• "North" is now in the negative y direction (upwards on GUI, which is more accurate). Affects season placement and neighbor naming.
• Standardizes find*Neighbor() functions to look the same as findNorthNeighbor().
• Removes unused variables in sugar and spice peak generation.

[nkremerh]

Going to add testing and validating this as an exercise for the first week of research work. Stay tuned.

[nkremerh]

Confirmed nearly identical trends across 50 seeds out to 1k timesteps.

[colinhanrahan]

Note: determinism with the current repo is maintained without the north-south switch. The only difference with the north-south switch is that the order of neighbor cells is slightly different, so it will still be slightly different after shuffles.