* refine yolov3/rcnn/ssd dataset download

* refine docs

* modify PaddleRec readme

* add face doc
* update face detection readme and add demo jpg

This reverts commit 5108c1c1.

* refine download sh to py

* update QUICK_STARTED

* add quick download link of bos in README.

fix the wrong indents in the menu

update the readme of PaddleNLP, showing the new features of Paddle 1.6, making it easier to be understood, and making it colorful, to be alive.

* Remove KD scripts

* Add ERNIE2.0 service

* Update server

* Update MTL

* Update README.md

* Update README.md for MTL

* Update README.md

* upgrade_dmtk_name

* Add C++ inference solution.
* Correct the link.

* Error out if fp16 is enabled and affine channel is used

* Add more documentation on mixed precision training

* Remove KD scripts

* Add ERNIE2.0 service

* Update server

* Update MTL

* Update README.md

* Update README.md for MTL

* Update README.md

* Add beam search for dygraph Transformer.
Re-organize dygraph Transformer.

* Add custumed data support for dygraph Transformer.

* Add validation in dygraph Transformer.

* Update notes for multi-gpu for dygraph Transformer.

* Revert "add check version (#3530)"

This reverts commit 2a167ec9.

* Revert "Upgrade API for gnn (#3503)"

This reverts commit 80b01801.

* Revert "upgrade API for DIN (#3499)"

This reverts commit 734812c3.

* add aistudio link in README

* add multi-scale test

* add modes and documents for vehicle and pedestrian detection

* remove needless output images

* add class names

* add Configure for training

* fix table in READ.md

* compress the images in the demo/output

* change the score_threshold for vehicle inference

* change Yolo v3 to YOLOv3

This reverts commit 0be3697c.

* add class aware sampling strategy
* remove redundancy code

This reverts commit 36a2e65b.

* Revert "change PyReader to from_generator (#3490)"

This reverts commit d331b799.

* Update data_reader.py

* Update data_reader.py

* Update utility.py

This reverts commit 04bfe0a8.

This reverts commit b591cc13.

* refine assert info in roidb_source.py

* refine image_dir assert

* fix fluid.data and fluid.io.DataLoader

* add logger in utils/utility.py