Introducing access log including refactoring for server side logs

[hwshim]

[gotchazipc]

1. we need a new logging api to support multiple (hierachical) loader, dealing with mulit-process env using nodejs' cluster module.
2. webida clients may need similar (or same) logging api that supports hierachical logging

this issue cannot be solved so easily. we'll create a new API and partially apply it in 1.7.0