Fix hang bug in parallel_map.py when multiprocessing mode used and some consumer exit abnormally (#106)

* Update GETTING_STARTED_cn.md
* Update x2coco.py

* fix mixup error when dataset has only 1 sample

* refine log

* change fluid.layers.data to fluid.data

* fix export_model doc

* Optimize data transforms for yolo training

* Simplify and add docstring

* update code & doc

* change voc_loader

* add x2coco.py

* Update DATA.md

* Update DATA_cn.md

* fix the labelme2coco.py

* fix the labelme2coco.py

* add multi-scale test

* add class aware sampling strategy
* remove redundancy code

* refine assert info in roidb_source.py

* refine image_dir assert

* Add face detection configs and main code.
* Integration multi-scale evaluation.

* add CropImageWithDataAnchorSampling
* Refine bbox sampling code
* Update comments
* fix import and variable problem

* Add backbone and architecture for FaceBoxes and Blazeface.
* Add dataloader for WIDERFace dataset.

* Support finetune by custom dataset

* add finetune args

* add load finetune

* reconstruct load

* add transfer learning doc

* add fruit demo

* add quick start

* add data preprocessing FAQ

* fix rcnn eval on voc

* update comment

* fix bug in sharedmemory
* fix bug in sharedmemory

* add a global norm_type flag

* add group norm on fpn

* add gn on box head

* add faster rcnn fpn 50 gn config

* add mask branch norm

* update configs

* Add full configs example & refine doc

* refine docs

* add_ssd_config_demo

* add_license for PaddleCV

* update license date

* update GAN license date

# Add VGG-SSD on VOC and COCO dataset.
# Add config and model zoo. 
# Refine bbox2out and draw_bbox:
    - Add bbox de-normalize in bbox2out function.
    - Remove bbox de-normalize in draw_bbox.

* fix yolov3 voc eval in train

* fix comment

* standard SENet and add a warning in coco loader