Description of changes:
1) Changed the campaign name: "Change of Eras" -> "New Era".
2) Changed the name of the third mission: "Battle at the Celestial Gates" -> "Last Stand" (the old name was displayed incorrectly in the game menu).
3) Applied the visual changes that I made for the second campaign.
4) The campaign is now fully compatible with the first two campaigns, as well as with the original campaigns and scenarios.
5) In the first mission, I increased the interval for the appearance of AI heroes.
6) In the third mission, I refined the combat scripts and removed a bug that caused the combat scripts to not work during defense.
7) Other minor changes.