Add backward doc and comments

Feature/rnn gradient check

Refine the activation type in the GRU operator related

Refine cos-sim-op

Adam selectedrows and scatter functors

update alexnet inference benchmark data on MKL

fix inference crash of alexnet benchmark

add paddle version of pip install and docker

* add helper function to get appropriate DeviceContext

GemmConvMobileFunction(optimized for mobile)

auto set openblas env

Feature/check nan executor

Feature/is nan

fix build link rt