Add exploration weights and calculator

[lucas-deangelis]

Here are the calculations:

The four locations (City, Snowfield, Forest, Wasteland) each have a starting weight of 10. A pet's affinity increases the weight of its associated area by 20. For example:

No pet: 10/10/10/10 = 25%/25%/25%/25%

1 Dog: 10/30/10/10 = 16.7%/50%/16.7%/16.7%

2 Dogs: 10/50/10/10 = 12.5%/62.5%/12.5%/12.5%

3 Dogs: 10/70/10/10 = 10%/70%/10%/10%

1 Dog + 1 Cat: 30/30/10/10 = 37.5%/37.5%/12.5%/12.5%

1 Dog + 1 Cat + 1 Bird: 30/30/30/10 = 30%/30%/30%/10%