uniform logger manager in FleetAPI.
hidde API under distributed/utils which users don't need.

* reconstruct_of_fleet_api

* update

* fix bugs of reducer

* update

* update

* use yapf to format all python file

* yapf exclude two unittests file for they rely on writing and reading file, and format will break them

* disable diff_py_file because too many diff files cause command following failed

* remove unrequired ut cases

* update

* fix bugs

* update

* fix bug of check_inf

* fix allreduce

* Add solutions to PyLayer which is unsupported in DataParallel

* modify note format for parallel.py

* modify docs of dataparallel

* add docs of dp with pylayer

* modify docs format

* modify example format

* change example of dp with pylayer

* add unittest for dp with pylayer

* modify ut

* merge latest codes

* update

* modify for CI-Coverage

* modify text-indent

* dygraph sharding

* update unitest hybrid_parallel_communicate_group

* fix precision of mp

* fix bug of seed

* fix dp

* print group

* fix model parallel

* rm parallel_help.py

* add embedding

* add clip/check

* add amp & clip grad in dygraph

* add logging

* support dp & mp