Provide a GetUnitInternalCargo function in the API

[mousepilot]

Hi everyone,

Currently, we have in the API a setUnitInternalCargo function that allows us to set the "mass" in kilograms of cargo to add to a unit.

Unfortunately, there is no way to retrieve the current "mass" of the cargo inside a unit.

In some cases, we can track in the scripts the cargo mass of a particular unit, but in cases where other 3rd-party scripts may have added cargo to a unit, tracking the cargo mass becomes impossible.

If you can provide a getUnitInternalCargo, then a script creator can "add" or "remove" just the mass of the cargo he intends and leave any existing mass in the unit untouched.

Thank you.