Feature Request: Colourblind friendly IFF support.

Currently, the iff_defs.tbl only permits adjusting targeting colours. Whilst this is pretty neat, there's two or more things that are missing.

The first is: Permit alternative IFF colour sets to be defined. For example, something that allows people who are red-green colourblind to select a colour set that differentiates friend from foe by using a blue-red scheme instead.

For example, instead of
```
$IFF Name: Friendly
$Color: ( 0, 255, 0 )
```

Permit something like
```
$IFF Name: Friendly
$Colors
+Color1: ( 0, 255, 0 )
+Color2: ( 0, 0, 255 )
```
Users would then be able to select colour sets "1 or 2" in the options menu. Maybe also allow names for these to be defined... somewhere?

Alternatively, allow alternate colour sets to be defined that don't involve setting colors for each different team individually, instead using the simple logic of:
If on the same team, display this colour else
if on the attacks list, display this colour else
if not on the same team but not in the $attacks list, display this colour.
So you'd get table entries like
```
$Color set: Blue-Red
+Own Team: (0,0,255)
+Attack: (255,0,0)
+No Attack: (255,255,0)

$Color Set: Monochrome
+Own Team: (0,0,0)
+Attack: (255,255,255)
+No Attack: (0,0,0)
```
---

Secondly: Allow altered targeting brackets, icons, or even text to differentiate friend from foe in the HUD. Ideally, literally everything in the HUD that uses colour-coding should have some alternative that allows differentiation for people who can't see *any* colours. Thinking along the lines of

- Simply rotating a lot of HUD elements 45 degrees in-engine when an entity is targeted - like how NATO uses rectangular icons for friendlies and diamonds for hostiles.
- Rendering radar icons upside down for enemies
- Simple text string displayed as part of the targeting info - eg [F] Alpha 2, [H] Capricorn 1.
- Disabling certain hud elements when an entity on the player's team is targeted - eg don't display lead indicators.
- Replacing or dispaying new hud elements when an entity on the player's team is targeted, like replacing the crosshair with a different graphic.
- Dotted, shaded, or doubled lines