Implement loglevel and logfile config values

<a href="https://github.com/jachym"><img src="https://avatars.githubusercontent.com/u/1460823?v=3" align="left" width="96" height="96" hspace="10"></img></a> **Issue by [jachym](https://github.com/jachym)**
_Tuesday Jan 12, 2016 at 20:46 GMT_
_Originally opened as https://github.com/PyWPS/pywps-4/issues/81_

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does not seem to be implemented anywhere, still useful config value
