* Implement Int8 FC

* Integrate FC into INT8v2

test=develop

* int8 FC: transpose weights before computing scales

test=develop

* Add support for activation_type string in FC

test=develop

* Disable MKL-DNN's FC in VGG16 and 19

test=develop

* Disable FC quantization when mkldnn FC is disabled

test=develop

* Solve PADDLE_ENFORCES in FC int8

* Fix Paddle enforces and remove const cast

test=develop

* Fix style changes

test=develop

* Fix quantizer_tester test and add fc quantization

test=develop

* Fix FC test fail on CUDA

* Remove unnecessary log from quantize placement pass

test=develop

* Add Thread ID to FC hash key

test=develop

* Add comments to MKL-DNN FC Kernel

test=develop

* Refactor quantizer

test=develop

* Fix linter issues

test=develop

* Fix crash in slim googlenet

test=develop

* Fix PADDLE_ENFORCE messages

test=develop