* add get_last_save_xbox_base/get_last_save_xbox * fix fleet_util bug of load paddle model * add doc string in fleet api
* fix default value of fleet desc, default values are same with jingpai * print log when save model
* add fleet util (fleet/utils/fleet_util.py): functions for users' convenience * add some interface in hdfs util : hdfs is_file、hdfs cat
