* don't re-generate header file if content doesn't change. test=develop

* add copy_if_different function. test=develop

* polish grad op check, test=develop, test=document_fix

* keep op_use_default_grad_maker.spec to avoid conflict, test=develop, test=document_fix

* refine API.spec, test=develop

* add nn.py to test,test=develop

* fix by removing new.spec, test=develop, test=document_fix

* refine scripts when PYTHON_ABI is empty, follow partial comments, add extra cpp api doc, test=develop, test=document_fix

* remove extra doc changes, remove API.spec, test=develop

test=develop

test=develop

test=develop

* set the right shape of selected_rows
test=develop

* enhance check

* fix activation_op

* remove cast

* use ShareDimInfo replace SetDim and ShareLod

* use ShareDimAndLod
test=develop

* follow comment

test=develop

* check whether the input has lod
test=develop

* Split ShareDimAndLod

test=develop

* checkout clip.py
test=develop

* remove patchelf in windowls

* "follow comment"

move paddle/pybind/pybind.h to paddle/fluid/pybind/pybind.h, and cancel the test_parallel_op temporary

* write versino.py

* add version py

* clean init py

* add istaged, major and etc... fields

* update

* update

* update

* fix gitignore

* refine cmake file

* init commit

* change some dir name

* Add `dump_to_file()` for ProgrameDescBind in pybind

* Update

* Add utility.py

* typo

* Fix bugs

* Move add_feed/fetch_components to untility.py

* Compelete dump

* Follow comments

* Change output of Prune() from inference to pointer

* Expose Prune() to Python

* Compelete save/load API of inference model

* Fix errors

* Debuging

* Compelete unit tests

* follow comments

* Also use `const DeviceContext&` all the time, to prevent `const_cast`

Fix #4169
Fix #3468
Fix #3475

* Although backward_test/rnn_test is not pass, just comment them.

* Server recovery from checkpoint

* Expose paddle.framework by pybind11

* Export paddle.framework.{Scope, Variable} to paddle.v2.framework.core.
* See python/paddle/v2/framework/tests/test_scope.py for Python usage
* See paddle/pybind/pybind.cc for C++ bind code.

* add copyright

* added mnist demo

* modified .gitignore for .project files

* normalize pixel in mnist_provider.py and set use_gpu=0