Scheduled dispatch: Add company setting to set default schedule duration

src/settings_type.h

@@ -834,6 +834,7 @@ struct CompanySettings {
 	bool advance_order_on_clone;             ///< when cloning a vehicle or copying/sharing an order list, advance the current order to a suitable point
 	bool copy_clone_add_to_group;            ///< whether to add cloned vehicles to the source vehicle's group, when cloning a vehicle without sharing orders
 	bool remain_if_next_order_same_station;  ///< if the next order is for the same station, start loading/unloading again instead of leaving.
+	uint16 default_sched_dispatch_duration;  ///< default scheduled dispatch duration
 
 	byte old_simulated_wormhole_signals;     ///< no longer needs a setting: tunnel/bridge signal simulation spacing
 };