Allow to change logdir/logfile path

- Provide single configuraiton option `logDir/logPath` in `config.yml`.
- Move `log4j.json` into `logger.js` like https://gist.github.com/tomaszdurka/c89886d2f7b9e926e5cf
Maybe rather:
```js
var logger = require('../logger');
var log = logger.getLog()
```
or
```
var logger = require('../logger').getLog();
```