AI will not attack cities with no health with siege units

AI will not attack capturable cities with melee units that cannot capture them

Mod checker: conditional tags are accepted as "filtering uniques"

By RobLoach:
- Add Countable: `Adopted [policy] Policies by [civ] Civilizations` 
- Allow Buildings to increase Air Unit Capacity 
- Add Victory Type-specific music 

Disable automatic counter-denunciation for human players - By unciv-loof

By Ambeco - error handling works in edge cases