Add setting for linkgraph times to be in non daylength scaled days.

Savegame format change for link graph jobs.
Change link graph scheduler to support more than one operation
per day, on _date_fract ticks other than SPAWN_JOIN_TICK.

src/settings_type.h

@@ -550,6 +550,7 @@ struct EconomySettings {
 struct LinkGraphSettings {
 	uint16 recalc_time;                         ///< time (in days) for recalculating each link graph component.
 	uint16 recalc_interval;                     ///< time (in days) between subsequent checks for link graphs to be calculated.
+	bool recalc_not_scaled_by_daylength;        ///< whether the time should be in daylength-scaled days (false) or unscaled days (true)
 	DistributionTypeByte distribution_pax;      ///< distribution type for passengers
 	DistributionTypeByte distribution_mail;     ///< distribution type for mail
 	DistributionTypeByte distribution_armoured; ///< distribution type for armoured cargo class