* update 2.0 public api in vision

* fix some flake8 errors

* add two attributes for yolo box

* Fix slow data reading, In the old version, one epoch read time of this data set was about 5371 seconds(MacBook Pro Retina, 13-inch, Early 2015 2.7 GHz), and a batch took 211 seconds, It's too painful to use. Now decompress the data in advance (about 10 seconds). Each epoch of reading takes about 3 seconds(MacBook Pro Retina, 13-inch, Early 2015 2.7 GHz), and a batch takes 0.017 seconds more.

* Run CI, test=allcase

* fix qq group number. test=document_fix

 fix qq group number. test=document_fix

* fix qq group number. test=document_fix 

fix qq group number. test=document_fix

* add to_grayscale, normalize

* add rotate

* add vfip and hflip

* add crop center_crop


* add padding, support constant, reflect, replicate, circular same as paddle.pad

* add get-image-[n,c,w,h] axis utils

* add op read_file and decode_jpeg

* fixed docs.

* Fixed docs. test=document_fix

code bak.

fixed docs. test=document_fix

* Revert to previous version of python/paddle/fluid/backward.py

* fixed bugs.

* test=document_fix. Fixed examples.

* Support list and tuple for parameters of layer_norm, multiprocess_reader, DatasetFolder and ImageFolder.

* add unittest for layer_norm.

* add require gpu for example.

* Modified params of some APIs to support tuple and list.

* fixed bug.

* update comments

* add attrs deformable_groups

update RandomHorizontal Flip random description and examples

* fix test_datasets unittest

* update document of paddle.vision.dataset, test=document

* update document of paddle.vision.dataset, test=document

* update voc url

* fix cv2 rotation

* update to_tensor en docs

* add deform_conv2d,DeformConv2D

* Update Cifar Codes

* Update VOC2012 Codes

* Update voc2012.py

* Update voc2012.py

* Update cifar.py

* Update cifar.py

* Update voc2012.py

* lazy import for scipy

* rm unused check

* alias yolo_loss & decode_yolo_box to paddle.vision. test=develop

* add arg for vgg

* fix vgg num classes

* rm cv2 dependence of normalize

* return pil image as default according backend

* update hapi predict interface

* fix code style

* fix docs

* fix docs

* fix docs

* update docs

* fix codes style

* fix unittest

* fix unittest

* fix coverage

* rename manual_seed to seed

* rename xxx1d-->xxx1D, xxx2d-->xxx2D, xxx3d-->xxx3D

* rename manual_seed --> seed

* do not rename .cc, .cu and .h file

* rename manual_seed --> seed

* rename manual_seed --> seed

* rename manual_seed --> seed

* rename manual_seed --> seed

* disable_static on doc example code

* donot change manual_seed on generator

* add enable_static on sample code

* convert python/paddle/fluid/layers/nn.py to bak

* fix typo

* fix code style

* fix seed to manual_seed when call functions of Generator()

* fix bug

* add pil backend

* fix hapi load

* refine vision models