Research: allow overriding research duration for specific player with ActorInit

[michaeldgg2]

It is possible that map author might want to have some technologies pre-researched (e.g. player already starts with a base with research center). Currently we don't have any way to do this; we could override Researchable.Duration, but that's global and we need it per-player.

Implementation-wise it's likely necessary to do it on Researches trait (i.e. trait placed on Research Center), because it's not possible to define ActorInit objects for PlayerActor.