Add 4.5.0 changelog and docs

Change-Id: I07ec0a197de8a625788a3b0485d5ecf237e554ba
Reviewed-on: http://gerrit.cloudera.org:8080/22576
Reviewed-by: Zoltan Borok-Nagy <boroknagyz@cloudera.com>
Tested-by: Peter Rozsa <prozsa@cloudera.com>
611 files changed