* Simplize system_allocator and fix GPU_INFO

* Remove main_program/startup_program

* Fix optimizer

* Fix CI

* Follow comments

* "add asnumpy interface"

* Just for unittest

* Change unittests for numpy I/O

* Fix CI

* Change all `data_type` in Python to `dtype`

* Change `date_type` in C++ to `dtype`

* Refine

* Forward of raw if-else op

* add backward part of mnist if-else unittest

* refine fill_constant_batch_size_like layer

* add draft ifelse operator

* Complete IfElse Op

* add unittest of ifelse api

* merge baidu/develop

* Stash

* Merge develop branch

* Support int/int64 for fill_constant_batch_size_like