Prerequisite technology trigger

[Shemp]

This would be a simple new type of trigger: PrerequisiteTechnologyTrigger, which only has type = "prerequisite" in its table.

Technologies with this trigger would automatically be completed for free when the final prerequisite is completed. If it's defined with an empty/nil prerequisites array, or all of the prereqs are hidden, the technology is awarded to the force at the beginning of the game.

It would make suggestions like this one possible by composing three different trigger techs.

EDIT: And yes, I know you can do this with "scripted" triggers, but it would be nice to have a proper way with good performance.

-----------

Additionally, it could also be nice to define a count property so only some of the prereqs need to be completed. I don't know if the technical situation has changed since the official reply to this thread suggested that optional prereqs are unlikely to happen.

For instance, you define a tech that depends on completing Vulcanus, Gleba and Fulgora but with count = 2, so you'd only need to go to two planets to trigger the technology.