This file is here to allow devs to easily add stuff in the release notes for the next release, it allows easy syncing with the release team, since you don't have to be around when the release takes place... Just dump whatever you want to have mentioned in the release notes here. Please take care that it is in a way that allows copy&paste to the release notes. That is making sure that spelling/grammer/whatever is usable and that you are using complete sentences, not just single words. The release team should empty this file after each release. Terrain graphic rules for user-made add-ons are now loaded before the core ones, making custom tiles look the same in-game as they did in the editor in the previous release (1.5.2).