Feature/r2.5.2 release notes

Added CDAP-599 as a known issue. https://issues.cask.co/browse/CDAP-599
I think we shouldn't mention the MovieRecommender app in CDAP release note. It can be mentioned in the MovieRecommender README, saying that it doesn't work with 2.5.2 until the app is fixed (there is PR already opened for that).