Items payload support

[osipxd]

API

• Add MimicApiLevel class to check current running Mimic API version:

  // Specify here the version required for APIs you use.
  if (!MimicApiLevel.checkApiLevel(MimicApiLevel.VERSION_0_6)) {
      println("At least Mimic 0.6 is required. Please download it from {link here}")
  }

• Add optional payload to ItemsRegistry.getItem. It may be used to customize items.

Bukkit Plugin

• Add statistics about used items registries
• Add payload support to MinecraftItemsRegistry.