Merge pull request !5172 from riemann_penn/remove_name_args_from_gradoperation

Merge pull request !3394 from XunDeng/pp_poc_v3

update logic for cache

clean up code

add test cases for new api

update include of code

specify the resolve attr to ClassMember

avoid resolve attr of self

added cdf, logcdf, survival, logsurvival, entropy, mode, cross_entropy wrapper

Merge pull request !3230 from riemann_penn/add_bprop_for_sparse_tensor

Bernoulli and Normal

Merge pull request !236 from wuxuejian/incu_embedding

move embeddinglookup to the internal

- It provides a unified style to express graph and kernel for user.
- It provides a unified IR to represent graph and kernel for developer.
- It breaks the boundary between graph and kernel.
- It provides more opportunities to do compile optimization.

Merge pull request !150 from yanzhenxiang2020/add_rnnt_and_categorical