support parsing ascend rank table file

Destroy session first.

Add distribution supported

* update, test=develop

* upgrade comment string to raw string

* fix string in

* fix string with ' '

* revert update on comments

* upgrade only necessary

* fix sample code checker

* fix comments with '''

* test=develop, bug fix for parameter_recv
* test=develop, for unittest, test_fleet_rolemaker_new

* refine fleetrun.ps_launch

* update fleet run for multi device support

* ps_graph support ps-gpu

* fix heter save

* add heter save unittest

* fix unittest & simple code

* update fleetrun

* fix fleetrun

* fix launch barrier

* fix role maker

* add paddlecloud rolemaker unittest

* rename heter_worker_device_guard

* add gloo initializer, test=develop

* test=develop, bug fix

* fix worker endpoints

* fix gloo wrapper for hdfs

* GPU fleetrun support gloo

* parameterserver fleetrun support gloo

* fix get server endpoint

* test=develop, util documents

* fix ports conflict when launching multi-nodes in paddlecloud;test=develop

* add DISTRIBUTED_TRAINER_ENDPOINTS env for cloud;test=develop

* print detailed and clear log infos; test=develop

* move paddle.fleet to paddle.distributed.fleet

* support multi-ps training mode for fleetrun; test=develop

* add fleetrun command for distributed running; test=develop