Implement CheckCommand for Checkers not having Check perm

CommonCore/SQL/src/de/steamwar/sql/GameModeConfig.java

@@ -151,7 +151,7 @@ public final class GameModeConfig<M, W> {
      *
      * @implSpec {@code []} by default -> denoting every person with {@link UserPerm#CHECK} can check it
      */
-    public final List<Integer> Checkers;
+    public final Set<Integer> Checkers;
 
     /**
      * Bundle for countdowns during the fight
@@ -246,7 +246,7 @@ public final class GameModeConfig<M, W> {
         }
 
         CheckQuestions = loader.getStringList("CheckQuestions");
-        Checkers = loader.getIntList("Checkers");
+        Checkers = loader.getIntSet("Checkers");
         Times = new TimesConfig(loader.with("Times"));
         // Arena would be here to be in config order but needs Schematic.Size and EnterStages loaded afterwards
         Schematic = new SchematicConfig<>(loader.with("Schematic"));

CommonCore/SQL/src/de/steamwar/sql/YMLWrapper.java

@@ -139,6 +139,12 @@ final class YMLWrapper<M, W> {
         return get(path, o -> (List<Integer>) o);
     }
 
+    public Set<Integer> getIntSet(String path) {
+        List<Integer> list = get(path, o -> (List<Integer>) o);
+        if (list.isEmpty()) return Collections.emptySet();
+        return Collections.unmodifiableSet(new HashSet<>(list));
+    }
+
     public List<SchematicType> getSchematicTypeList(String path) {
         List<String> list = getStringList(path);
         if (list.isEmpty()) {