Reimplement aircraft carriers and rocket launchers from Red Alert 2

[ZivDero]

This PR reimplements SpawnManagerClass from Red Alert 2, used for aircraft carriers and rocket launchers.

In RULES.INI:

[SOMETECHNO]        ; TechnoType
Spawns=             ; AircraftType, the type that this Techno spawns.
SpawnsNumber=0      ; integer, the number of aircraft that this Techno spawns.
SpawnRegenRate=0    ; integer, the time it takes for a spawn to regenerate after death.
SpawnReloadRate=0   ; integer, the time it takes for a spawn to reload its ammo and restore its strength.

• Additionally, it's possible to specify an alternative voxel model to use when the spawner has no spawns docked.

In RULES.INI:

[SOMETECHNO]        ; TechnoType
NoSpawnAlt=no       ; boolean, should this Techno use an alternate voxel model when it's out of spawns?
                    ; When true, the model named SOMETECHNOWO will be used when it's out of spawns.

`NoSpawnAlt` is only available for Technos that use voxel models.

Unlike in Red Alert 2, the voxel model used by `NoSpawnAlt` is loaded into a separate area of memory from the turet model. This means that Technos that have `NoSpawnAlt=yes` set **can** have turrets.

• For the unit to create spawns upon attack, a flag needs to be set on its weapon.

In RULES.INI:

[SOMEWEAPON]  ; WeaponType
Spawner=no    ; boolean, does this weapon spawn aircraft when firing?

Rockets

• For rocket launchers to function, RocketTypes need to be defined.

In RULES.INI:

[RocketTypes]
0=SOMEROCKET

[SOMEROCKET]            ; RocketType
PauseFrames=0           ; integer, how many frames the rocket pauses on the launcher before tilting.
TiltFrames=60           ; integer, how many frames it takes for the rocket to tilt to firing position.
PitchInitial=0.21       ; float, starting pitch of the rocket before tilting up (0 = horizontal, 1 = vertical).
PitchFinal=0.5          ; float, ending pitch of the rocket after tilting up before it fires.
TurnRate=0.05           ; float, pitch maneuverability of rocket in air.
RaiseRate=1             ; integer, how much the missile will raise each turn on the launcher (for Cruise Missiles only).
Acceleration=0.4        ; float, this much is added to the rocket's velocity each frame during launch.
Altitude=768            ; integer, cruising altitude in leptons (1/256 of a cell): at this height rocket begins leveling off.
Damage=200              ; integer, the rocker does this much damage when it explodes.
EliteDamage=400         ; integer, the rocker does this much damage when it explodes when the spawner is elite.
BodyLength=256          ; integer, the length of  thebody of the rocket in leptons (1/256 of a cell).
LazyCurve=yes           ; boolean, is the rocket's path a big, lazy curve, like the V3 is Red Alert 2.
CruiseMissile=no        ; boolean, is this rocket a Cruise Missile, like Boomer missiles in Yuri's Revenge.
Type=                   ; AircraftType, the type this rocket is associated with.
Warhead=                ; WarheadType, the warhead that this rocket's explosion uses.
EliteWarhead=           ; WarheadType, the warhead that this rocket's explosion uses when the spawner is elite.
TakeoffAnim=            ; AnimType, the takeoff animation used by this rocket.
TrailAnim=              ; AnimType, the trail animation used by this rocket.

The rocket object is an AircraftType, like in Red Alert 2. When determining its characteristics, the rocket will use the first RocketType whose `Type=` is equal to the type of the rocket itself.

• Additionally, for rocket launchers that launch two rockets at a time, a second spawn offset can de defined.

In ART.INI:

[SOMETECHNO]             ; TechnoType
SecondSpawnOffset=0,0,0  ; 3 integers, an offset to be added to the firing FLH for the second missile's location.