NS4: Allow changing object lifetime

[dennwc]

So that it's possible to capture FoN/DeathBall mid-flight and prolong its lifetime.

[dennwc]

Intermediate result - FoN is created as a regular object without any lifetime. Instead, the spell that runs it has a duration, as if it was channeled. When duration runs out - it destroys the ball. So for this use case to work we'll need to expose DurationSpell, which is a bit too deep (implementation detail).

If above will be confirmed, we should make a NS4 sub-package for exposing spells with custom parameters. That way we could expose FoN lifetime as a spell configuration.