Add Item Legacy Support

SpigotCore_Main/src/de/steamwar/inventory/SWItem.java

@@ -154,7 +154,11 @@ public class SWItem {
                 item = new SWItem(Material.valueOf(itemJson.get("material").getAsString()), itemJson.get("title").getAsString());
             }
         }catch (IllegalArgumentException e) {
-            item = new SWItem(Material.STONE, itemJson.get("title").getAsString());
+            try {
+                item = new SWItem(Material.valueOf(Material.LEGACY_PREFIX + itemJson.get("material").getAsString()), itemJson.get("title").getAsString());
+            }catch (IllegalArgumentException ex) {
+                item = new SWItem(Material.STONE, itemJson.get("title").getAsString());
+            }
         }
         if(itemJson.has("skullOwner")) {
             item = SWItem.getPlayerSkull(itemJson.get("skullOwner").getAsString());