Improvements for json validation for mods

- Implemented validation for `targetCondition` in spells
- Implemented validation for `mapObject` in towns/heroes
- Fixed validation of zone connections in RMG
- Added workarounds to prevent assertions triggering on invalid mods
- Erase 'base' entries from json before validation (but after applying
them to derived keys)

Should have no effect on mod behavior/support, but may cause new
detections for mods that were broken in either 1.6 or 1.7

lib/mapObjectConstructors/CObjectClassesHandler.cpp

@@ -356,6 +356,12 @@ void CObjectClassesHandler::loadSubObject(const std::string & identifier, JsonNo
 	}
 
 	JsonUtils::inherit(config, mapObjectTypes.at(ID.getNum())->base);
+	for (auto & templ : config["templates"].Struct())
+		JsonUtils::inherit(templ.second, config["base"]);
+
+	if (settings["mods"]["validation"].String() != "off")
+		JsonUtils::validate(config, "vcmi:objectType", identifier);
+
 	loadSubObject(config.getModScope(), identifier, config, mapObjectTypes.at(ID.getNum()).get(), subID.getNum());
 }