Cannot have multiple PatternTimetables referring to same source trip in AdjustFrequency

[mattwigway]

In AdjustFrequency, all PatternTimetables get put in a map from sourceTripId to PatternTimetable, which means that there can only be one entry per trip ID. This is problematic if you want to have multiple frequencies over the day.

Also, we will have to split TripSchedules because it's possible to have different pattern entries with the same source trip and different service (e.g. one is M–F and one is Saturday/Sunday). It's probably easiest to just create a TripSchedule per PatternTimetable.