feat(runner): added possibility to use module with params in onPrepare

The change allows to provide parameters to `onPrepare' method within the string, like:

```javascript
onPrepare: 'onPrepare/startupModule.js 12345'
```
startupModule.js content
```javascript
module.exports = function (args) {
    browser.params.password = args[0];
};
```