Polished allies03a

- added difficulties
- removed prisoner hack
- added a description in order to fix #7084 

PS: What about something like "As we don't want to engage (too many) soviet reinforcements,
I'll need your explicit orders to fire, Commander!" instead of "The area is crowded with civilians"?
```diff
-!IsCloaked(a)
+self.Owner.Shroud.IsTargetable(a)
```