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/entities/hero/CHeroClassHandler.cpp

@@ -123,9 +123,9 @@ std::shared_ptr<CHeroClass> CHeroClassHandler::loadFromJson(const std::string &
 	LIBRARY->identifiers()->requestIdentifier(scope, "object", "hero", [=](si32 index) {
 		JsonNode classConf = node["mapObject"];
 		classConf["heroClass"].String() = identifier;
+		classConf["heroClass"].setModScope(scope);
 		if (!node["compatibilityIdentifiers"].isNull())
 			classConf["compatibilityIdentifiers"] = node["compatibilityIdentifiers"];
-		classConf.setModScope(scope);
 		LIBRARY->objtypeh->loadSubObject(identifier, classConf, index, heroClass->getIndex());
 	});