Policy.rates for negative activities

[zanebclark]

If a Rule has a negative activity (e.g. no parking), what purpose would the Rule.rate array serve? Can we:

1. Clarify the purpose of a negative activity Rule.rate or
2. Document that a negative activity Rule.rate array should be empty

[schnuerle]

Good idea. Take a look at updates to the Rate.rule description, and the new sentence at the end of the Activities description.