#225 enable logging to different streams

1st step for #225 enable logging to different streams. The next step is to support application history based on this work.

Please first review this work.

<!-- Reviewable:start -->
[<img src="https://reviewable.io/review_button.png" height=40 alt="Review on Reviewable"/>](https://reviewable.io/reviews/intel-hadoop/gearpump/234)
<!-- Reviewable:end -->

Configs is a data class type, which store configuration items. It is not supposed to be used like this.