Add a 'Death Timer' function for units so that they take damage over time

As soon as a unit is created (e.g. through mutation, or built at a Barracks) it starts taking damage.

[MYUNIT]
Strength=200
ProduceDeathAmount=20 ;HP damage taken every delay
ProduceDeathDelay=100 ;frame delay

So this unit would die after 1000 frames (or less if it actually gets attacked as well)

This would be quite a versatile option (MAD tanks, zombies, etc)