Give ProgressiveKits the ability to not use xp or use crowns instead of gems for leveling

Plugins/Mineplex.Core/src/mineplex/core/progression/ProgressiveKit.java

@@ -285,4 +285,14 @@ public interface ProgressiveKit
 			  ViewDist.NORMAL, displayTo);
 		}
 	}
+	
+	default boolean usesXp()
+	{
+		return true;
+	}
+	
+	default boolean crownsEnabled()
+	{
+		return false;
+	}
 }