Integrate MLflow project

[nudles]

mlflow has a well defined format for a project, including the requirements.
Can we support mlflow projects (with models implemented following singa-auto Model API) on singa-auto?
If not, what are the issues?

[nudles]

There are some other tools for logging the results and visualization. https://www.zhihu.com/question/384519338/answer/1177727079