Added new crate unit types, way for mission maker to force faction in gear script call, vanilla-to-AGM medical items converter for cargo bearing entities.

Per file:

- f/assignGear/f_assignGear_(aaf/nato/csat/fia):
-- added new crate unit types to unit type list;
-- added three crate unit type cases to unit case list (sizes small, medium and large);
-- added check to see if passed _unit is a in class DEFAULT (ergo a cargo crate), check for medical system parameter, and if applicable convert items inside to AGM items.
- f/assignGear/fn_assignGear:
-- declare extra needed variables;
-- update clarification blurb at L31;
-- added check for (optional) extra variable and set _faction accordingly;
- f/medical/AGM_converter (new):
-- added new vanilla-to-AGM itemconverter (cargo only);
-- added dynamic checks for #FAK and #Medkit so can work on any unit type that has medical items in cargo;