Custom Skeleton Support - #3653

What type of PR is this.

1. Bug
2. Change
3. Enhancement

What have you changed and why?

Information:
Modder resource to allow for the creation of templates with custom skeletons (or more accurately, custom base units the game tries to spawn)

Please verify the following and ensure all checks are completed.

1. Have you loaded the mission in LAN host?
2. Have you loaded the mission on a dedicated server?

Is further testing or are further changes required?

1. No
2. Yes (Please provide further detail below.)

How can the changes be tested?

Steps: Load the attached template with OPTRE installed and get some SF to spawn, they will be Spartans with custom base units / skeletons.
Vanilla_AI_CSAT_Arid.txt

Notes:
Skeletons are defined per unit class, so you can make sure the SF Autorifleman has a custom skeleton and the SF Medic doesnt if you want, but it cannot be randomized. The input to the faction load for each unit class entry looks like
_unitLine params ["_name", "_template", ["_traits", []], ["_count", 5], ["_baseClass", ""]];
So the existing standard of [name, loadouts] needs to have extra nils added to add a custom base class. See example below:

private _unitTypes = [
    ["SquadLeader", _squadLeaderTemplate, nil, nil, "OPTRE_Spartan3_Soldier_TeamLeader"],
    ["Rifleman", _riflemanTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Rifleman_AR"],
    ["Medic", _medicTemplate, [["medic", true]], nil, "OPTRE_Spartan3_Soldier_Corpsman"],
    ["Engineer", _engineerTemplate, [["engineer", true]], nil, "OPTRE_Spartan3_Soldier_Engineer"],
    ["ExplosivesExpert", _explosivesExpertTemplate, [["explosiveSpecialist", true]], nil, "OPTRE_Spartan3_Soldier_Rifleman_AR"],
    ["Grenadier", _grenadierTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Rifleman_AR"],
    ["LAT", _latTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Rifleman_AT"],
    ["AT", _atTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Rifleman_AT"],
    ["AA", _aaTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Rifleman_AR"],
    ["MachineGunner", _machineGunnerTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Automatic_Rifleman"],
    ["Marksman", _marksmanTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Marksman"],
    ["Sniper", _sniperTemplate, nil, nil, "OPTRE_Spartan3_Soldier_Scout_Sniper"]
];

Loadouts are still applied as normal. So certain loadouts may need to be empty or have custom gear to support the skeleton.