Adding Bike and Walk Assignment

[bettinardi]

As part of the final results suite, ODOT would like to have the walk and bike demand assigned. ODOT understands that this would not be a calibrated routing assignment, but ODOT does have a desire to see the shortest path demand from the model on the all-streets (paths) network, to get a general sense of where bike and walk trips are occurring in the model.

The solution could either be a period based assignment added to the highway and transit model stream (each iteration), or (perhaps preferably) a more simplistic approach where at the very end a final daily assignment is completed and saved.

Whether the assignment is completed by period or daily; the link, connector, and zone level information from the assignment(s) need to be saved out to a text file (similar to the highway and transit assignment results), and then loaded into the final version file so that summary assignment information can be visualized.

This issue should be addressed after #83 so that the connector and zone tabulation back to the final version file is already worked out for the highway (and maybe Transit) elements.