Add sequence slice operator

remove redundant tests in layer helper's unittest.

Add the configuration helper for multi-head attention.

update the dot_product_attention.

Add the L2 distance layer.

* enforce shape of backward target to be {1}

* fix test_regularizer.py

* rm unused code

* fix backward_test

* fix a type bug

* fix test_program

fix compiler error in "WITH_MKL"

change message level from warning to status, and fix hard number in paddle version

add conv3d_trans_cudnn_op

[Speed compiling]: Refine cmake about CUDA to automatically detect GPU arch by default.

Fix data order of H0 in GRU Operator

add dot_prod_layer

rename all Mkldnn to MKLDNN

fix typo

enable mkldnn_concat layer

remove usused ProtoDataProvider related codes

add option WITH_MKL