* update config

* re-blacken python code

* temporarily disable date and diff_py_file

* skip a format

* 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

* parameter_server_optimizer support auto_strategy

* add auto parallel L1 implementation
test=develop

* fix api document

* consider the combination of different strategies to work together

* add check approval
test=develop

* move paddle.fleet to paddle.distributed.fleet

Add dgc to fleet meta optimizer, rm dgc from optimizer all

* refine strategy compiler and meta optimizers
make async as a_sync

refactor fleet api under paddle.fleet
update DistributedStrategy