add validation for building type instead of obscure error message

config/schemas/townBuilding.json

@@ -36,6 +36,7 @@
 		},
 		"type" : {
 			"type" : "string",
+			"enum" : [ "mysticPond", "artifactMerchant", "freelancersGuild", "magicUniversity", "castleGate", "creatureTransformer", "portalOfSummoning", "ballistaYard", "stables", "manaVortex", "lookoutTower", "library", "brotherhoodOfSword", "fountainOfFortune", "spellPowerGarrisonBonus", "attackGarrisonBonus", "defenseGarrisonBonus", "escapeTunnel", "attackVisitingBonus", "defenceVisitingBonus", "spellPowerVisitingBonus", "knowledgeVisitingBonus", "experienceVisitingBonus", "lighthouse", "treasury", "thievesGuild", "bank", "configurable" ],
 			"description" : "Subtype for some special buildings"
 		},
 		"mode" : {