title: unity engine bundle in .obb expansion pack
body: <p>I am using Unity engine.
  I want to make my app as .apk + .obb which the Unity does provide an option for.
  I also want to setup asset bundles which can be downloaded for game updates.</p>
  
  <p>Here are my questions </p>
  
  <p>1) can I pack asset bundles only into .obb. Are asset bundles packable into a .obb file ?
  2) I have a prefab in .obb file but I want to use a newer version in the asset bundle which I will download. How to know the version ? 
  3) Basically we use LoadFromCacheOrDownload to load the bundle. If a bundle is part of .obb can LoadFromCacheOrDownload() load that bundle from .obb as cache ?</p>