* add pretrained models

* fix typo

* add enable benchmark for lite

* fix config

* Updata "*" to "paddle.multiply"

* Update "+" to "paddle.add"

* Fix "tar" to "pdparams" to adapt to dygraph

* Update the download link of Paddle Inference Library

* Update faq_2020_s1.md

* Update faq_2020_s1.md

* Update faq_series.md

* add kunlun readme

* fix trt doc

* update history

* fix cpp time

* fix time

Fix some description of documentations

* support fp16 training

* Use compiled training program

* Change timing ips.

* Use dali

* add pure fp16 training

* fix a bug, which will not use fuse pass using pure fp16 training.

* modify code as review

* modify loss, so that it will use different loss when using pure fp16 training.

* remove some fluid API

* add static optimizer.

* fix eval script

* fix dali shell

* Add FAQ 20201207

* Fix FAQ20201207