Add test cases for nginx conf parser
Modify test code AND Add test cases to handle multiple add_headers
Add a new function get_custom_headers
Fix bugs in match_path_pattern
Handle the Cache-Control header properly
Integrate the new feature custom http header with leo_gateway
Enable to handle nginx time interval format(http://nginx.org/en/docs/syntax.html)
Merge branch 'feature/imple-issue239' into develop