Units can carry materials.
Table: unit-storage-x u m -> n
This table is the space reserved specifically for each
type of material.
Defaults to 0.
Materials that represent people may surrender to a unit in their cell.
Table: people-surrender-chance u t -> n%
This table is the base chance that people in terrain of type t
will change sides if a unit of type u is in their cell.
Defaults to 0.
Table: people-surrender-effect u m -> n
This is a multiplier that takes the people type into account.
Defaults to 100.