Implemented "EoHS with any era" [modification] for 1.11
A bunch of fixes from today's playtesting
Mostly eliminated reliance on underlying_id, after it broke 1.10 replays

shadowm tells me that using underlying_id in scripts is always bad.
I'm still using it for a few things where I think it's the most appropriate,
such as the game action simulations.
Cleaned up some animation smoothness issues