Add support for reading in lanes that have multiple turns

At this point, there may be cases where all the displayed lanes are green. For example, if you're taking a left turn at a standard (90-degree) intersection, and there's a right-turn island, then for the segment leading up to the island, all displayed lanes will be green.

This will be fixed later when support is added for having 90-degree turns with `turn:lanes` info displayed and when the turn lane information is copied to nearby intersections before the main turning intersection.
At that point, there shouldn't be any primary and secondary turns assigned, so the values at each index of `t.getLanes()` should be either 1 or 0.