This work is partially supported by
GDUPS (2012), National Natural Science Foundation of PRC (71271100, 71401057), Guangdong Social Science Foundation (GD13YLJ02), The Soft Science Project of Guangdong Province (2014A070704008), Collaborative Innovation Center of Scientific Finance & Industry, and Innovative Group Foundation (ITumanities and Social Sciences) for Higher Education of Guangdong Province (2015WCXTD009).