As promised: more cleanup, refactoring and testing of OSMGraphBuilder.

I've moved more of the string parsing logic out of the graph builder and into the OSMNode/Way/etc. classes. I've also added unit tests for much of this code. In addition, I added a new unit test of the OSMGraphBuilder that checks that the street and turn directionality constraints are applied equally to CAR and CUSTOM_MOTOR_VEHICLE. I will add more detailed testing of the OSMGraphBuilder in future.

As usual, everything builds and all tests pass.
Avi