Strong typedef: Use strong typedefs for date, date tick, minutes types

Add delta types
Adjust/add type conversion functions
Add various utility methods on types
Remove the various minute macros
Fix some minute conversion inconsistencies

src/departures_func.h

@@ -20,6 +20,6 @@
 DepartureList* MakeDepartureList(StationID station, const std::vector<const Vehicle *> &vehicles, DepartureType type = D_DEPARTURE,
 		bool show_vehicles_via = false, bool show_pax = true, bool show_freight = true);
 
-DateTicksScaled GetDeparturesMaxTicksAhead();
+Ticks GetDeparturesMaxTicksAhead();
 
 #endif /* DEPARTURES_FUNC_H */