[Model] add PFLD model (#433)

* support face alignment PFLD

* add PFLD demo

* fixed FaceAlignmentResult

* fixed bugs

* fixed img size

* fixed readme

* deal with comments

* fixed readme

* add pfld testcase

* update infer.py

* add gflags for example

* update c++ readme

* add gflags in example

* fixed for ci

* fixed gflags.cmake

* deal with comments

* update infer demo

Co-authored-by: Jason <jiangjiajun@baidu.com>

examples/vision/facealign/pfld/python/README.md

@@ -0,0 +1,71 @@
+# PFLD Python部署示例
+
+在部署前，需确认以下两个步骤
+
+- 1. 软硬件环境满足要求，参考[FastDeploy环境要求](../../../../../docs/cn/build_and_install/download_prebuilt_libraries.md)  
+- 2. FastDeploy Python whl包安装，参考[FastDeploy Python安装](../../../../../docs/cn/build_and_install/download_prebuilt_libraries.md)
+
+本目录下提供`infer.py`快速完成PFLD在CPU/GPU，以及GPU上通过TensorRT加速部署的示例，保证 FastDeploy 版本 >= 0.6.0 支持PFLD模型。执行如下脚本即可完成
+
+```bash
+#下载部署示例代码
+git clone https://github.com/PaddlePaddle/FastDeploy.git
+cd FastDeploy/examples/vision/facealign/pfld/python
+
+# 下载PFLD模型文件和测试图片以及视频
+## 原版ONNX模型
+wget https://bj.bcebos.com/paddlehub/fastdeploy/pfld-106-lite.onnx
+wget https://bj.bcebos.com/paddlehub/fastdeploy/facealign_input.png
+
+# CPU推理
+python infer.py --model pfld-106-lite.onnx --image facealign_input.png --device cpu
+# GPU推理
+python infer.py --model pfld-106-lite.onnx --image facealign_input.png --device gpu
+# TRT推理
+python infer.py --model pfld-106-lite.onnx --image facealign_input.png --device gpu --backend trt
+```
+
+运行完成可视化结果如下图所示
+
+<div width="500">
+<img width="470" height="384" float="left" src="https://user-images.githubusercontent.com/19977378/197931737-c2d8e760-a76d-478a-a6c9-4574fb5c70eb.png">
+</div>
+
+## PFLD Python接口
+
+```python
+fd.vision.facealign.PFLD(model_file, params_file=None, runtime_option=None, model_format=ModelFormat.ONNX)
+```
+
+PFLD模型加载和初始化，其中model_file为导出的ONNX模型格式
+
+**参数**
+
+> * **model_file**(str): 模型文件路径
+> * **params_file**(str): 参数文件路径，当模型格式为ONNX格式时，此参数无需设定
+> * **runtime_option**(RuntimeOption): 后端推理配置，默认为None，即采用默认配置
+> * **model_format**(ModelFormat): 模型格式，默认为ONNX
+
+### predict函数
+
+> ```python
+> PFLD.predict(input_image)
+> ```
+>
+> 模型预测结口，输入图像直接输出landmarks坐标结果。
+>
+> **参数**
+>
+> > * **input_image**(np.ndarray): 输入数据，注意需为HWC，BGR格式
+
+> **返回**
+>
+> > 返回`fastdeploy.vision.FaceAlignmentResult`结构体，结构体说明参考文档[视觉模型预测结果](../../../../../docs/api/vision_results/)
+
+
+## 其它文档
+
+- [PFLD 模型介绍](..)
+- [PFLD C++部署](../cpp)
+- [模型预测结果说明](../../../../../docs/api/vision_results/)
+- [如何切换模型推理后端引擎](../../../../../docs/cn/faq/how_to_change_backend.md)