* "add softmax cudnn functor support"

* "add testing"

* "refine cmakelist"

* "sequence softmax forward speed up"

* "add softmax grad"

* "fix sequence softmax test"

* "add double precision'

* "fix softmax test"

* "add softmax cudnn support"

* "fix softmax cudnn test"

* "add softmax to nn.py"

* "fix compile bug"

* "refine cmakelist"

* "fix ci"

* "fix based on comment"

* "fix based on comments"

* "fix ci"

* "exported scatter to python"

* Revert ""exported scatter to python""

This reverts commit 38745a62.

* "polish scatter and export to python"

* Generating random numbers with given batch size

uniform_random_batch_size_like_op
gaussian_random_batch_size_like_op

* More comments about random seed.

* Move test_*_random_batch_size_like_op to unittests

Impl scalar switch case op with condition op

* add basic interface for learning rate decay
* add exponential_decay
* add natural_exp_decay
* add inverse_time_decay

* "fix decode bug"

* "follow commnet"

* "fix error"

* "fix hook bug"

* fix based comment

* fix copyright

* fix based on comment

* registery is only used by layers
* Rename it to layer_function_generator

* add copyright hook

* add copyright hook

* refine copyright hook

* "test copyright hook"

* fix check style

* fix ci

Added backward.calc_gradient to backpropagate gradient from given targets to inputs.

* Make cast op support bool

Also add `elemwise_sub/mul/abs/clip` layers

* Make fuild.layers as a module

* Move layers as a module

* Split layers.py into layers module

* Fix CI

* Fix CI