Make NKAI default AI.

config/schemas/settings.json

@@ -335,7 +335,7 @@
 				},
 				"playerAI" : {
 					"type" : "string",
-					"default" : "VCAI"
+					"default" : "Nullkiller"
 				},
 				"friendlyAI" : {
 					"type" : "string",