This patch moves six structure actors (they're structures, not special):
- Ishtar gate from special/ to structures/babylonians/*
- pyramid from special/ to structures/egyptians/
- minor pyramid from special/ to structures/egyptians/
- stoa from special/ to structures/hellenes/
- great stoa from special/ to structures/hellenes/
- Babylonian tower from structures/persians/ to structures/babylonians/
and updates the simulation templates that use them accordingly. Also remove the Persian civ and name from the (unbuildable) Babylonian tower.
Yes, this creates two new structures/ folders with just two templates each; however, that's not unprecedented: mercenaries/ contains three files, thebans/ and viking/ one each.