refactor Passenger into more generic "Resource" (design)

[robfitzgerald]

a Passenger is a kind of thing of which Resource more broadly defines. in the case of Passenger, it is a resource with a pickup and dropoff location which takes up a passenger seat.

in order to allow HIVE to model food delivery / postal delivery / freight delivery problems, the Request concept needs to be made more generic. is the resource a passenger? does it allow_pooling? can it share a vehicle with other types of resources? does it have an expected delivery time? if the destination rejects it, can it be returned to it's origin?

1. consider the effects that could capture a broader "resource" type
2. consider what would need to change in the vehicle FSM
3. come up with a design for a Resource