add linspace op

* Enable INT8 Concat Kernel to improve the performance of MobileNet-SSD.
test=develop

* Optimize UT format.
test=develop

* Fix UT file address issue.
test=develop

* Refine the license year.
test=develop

* Optimize code for new API.
test=develop

* Restructure INT8 Concat kernel.
test=develop

* Rewrite gradient ProtoMaker for affine_channel_op to remove the Output as the input.
* Add act in Python API to make the act can be in-place by layer_help.py

* temoprarily disable the code of use kCUDNN, test=develop

* add TODO comment, test=develop

* Enhance affine_channel_op infer-shape check

* Add softmax_with_cross_entropy_op test=develop

* simplify implementation test=develop

* take care edge cases test=develop

* use pragma test=develop

* wip allreduce in op

* wip

* wip

* wip

* wip adding test

* wip for conflict with mp mode

* fix tests test=develop

* fix cpu build test=develop

* fix travis clang format test=develop

* fix cpu build test=develop

* update api.spec test=develop

* delete comment test=develop

* fix cpplint test=develop

* fix test=develop

* follow comment test=develop

* add file test=develop

* fix build test=develop

* update test=develop

* to be compatible with sync_bn, and fix mp mode in develop test=develop

test=develop

test=develop

test=develop

test=develop

* Enable INT8 transpose kernel for MobileNet-SSD improvement.
test=develop

* Refine the license year.
test=develop

* Delete redundant code.
test=develop

* Add axis check.
test=develop