Add Checkbox to Free Assigned Equipment

The checkbox would be on each truck and would "Free when idle" basically.

Logic: When you assign a truck to a facility, it will haul for that facility until there is not a load available (note: this should follow the option for partial or full loads). Once the truck has no more freight to haul for the facility and it would otherwise sit idle, auto-un-assign it.

Use case: Coal Supply is getting empty for the power facilities. Assign multiple trucks to that one container so they focus on hauling that product for that facility. However once they are caught up again, release them back into gen-pop.

The option should be on the truck, not the container. This way you could release 4 of the 5 trucks when they container is full, keeping one dedicated.