Add a GenericLocation class to represent to/from locations as well as intermediate points.
Modify RoutingRequest to keep the to/from/intermediate locations as GenericLocations. Factors the string parsing code out of RoutingRequest and StreetVertexServiceImpl.
Fix test that relied on types of RoutingRequest.from/to
Update code that relied on the RoutingRequest.from/to being strings.
Add a unit test for GenericLocation.