* Support softmax return in softmax_with_cross_entropy

* Add test for return_softmax=False

test=develop

test=develop

Density prior box operator for image detection model.

test=develop

test=develop

test=develop

test=develop

* add lod tensor array concat

* add lod tensor array concat

* test=develop

* add lod tensor array concat
test=develop

* Fix API.spec
test=develop

* add lod tensor array concat
test=develop

* revise some bug of lod tensor array concat
test=develop

* add unittest for tensor array concat
test=develop

* change to tensor array to tensor
test=develop

* revise bug
test=develop

* revise a bug
test=develop

* revise a bug
test=develop

* revise a bug of python3
test=develop

* exhaustive search for cuDNN conv.
* Refine code and add unit testing.
* Fix model load in fluid/inference and unit testing in conv2d
* Follow comments.
* Fix compiling test=develop

test=develop

the build strategy is finalized after create_passes. So future
change of build strategy has no effects.

test=develop

test=develop

* fix input<tensor>
test=develop

* fix split_ids
test=develop

* ElementwiseMul should not support SelectedRows

* fix scale op
test=develop

* change GetTensorFromVar() method to GetTensorOrSelectedRowsFromVar()

* fix operator

* refine MultiOutput

* fix MultiOutput
test=develop

* disable test_dist_save_load
test=develop

* fix elementwise_op
test=develop

* add get_sparse_as_op
test=develop

* add info for check
test=develop

* rename get_sparse_as_op with extract_rows_as_op.
test=develop

* elementwise doesn't support selected_rows

* fix regularizer

* remove extract_rows_as
test=develop

* fix ci
test=develop

* add test for sum_op

* fix regularizer
test=develop

*  test=develop

* fix pserver weight decay multi inputs test=develop

test=develop

test=develop

test=develop

test=develop

test=develop

recordio is not the official API in Fluid 1.0. Remove unittests for it.

test=develop

Dry run tests will skip `Op.Run` and just perform job scheduling. It helps to analysis dead lock in PE.

test=develop