Ruleset switching in new game screen no longer allows zero victory types

Users cannot offer negative gold with "-50" buttons

By unciv-loof:
- Notification shows who is responsible for skipping or resigning a player 
- Newly fetched mod entries respect current filter 
- Declaation of War + Declaration of Friendship UI improvements

By Ambeco:
- Fixed alternate pathfinding bugs 
- Unitactions and UnitTriggers have moddable priority
- Eliminated most Hardcoded Terrains