Large memory performance improvements for large maps  

Modding: show exact location of json file errors

By SomeTroglodyte:
- Context menu visual indicators 
- Modding: Fixed "empty name" problems 
- Fix expansion clearing barbarian camps leaving obsolete quests 
- City buy tile context menu, to buy several tiles at once 

Avoid centering on hidden wonder locations - By xplon

Respect alternative promotion prerequisites in validation - By superdusto