Added new crate unit types, way for mission maker to force faction in ge...

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;