Don't create default file directory on startup

In the `oae-content/config/storage.js` config file, there is this block of code:

```javascript
// By default, store the uploaded files on the same level as Hilary.
// Create the directory if it doesn't exist already.
var dir = path.join('..', 'files');
if (process.env['OAE_COVERING']) {
    dir = path.join('..', dir);
}
mkdirp.sync(dir);
var localDir = fs.realpathSync(dir);
```

This should not happen here, but it should be in a content init cycle once it knows what the configured directory is, then it can create it if it doesn't exist.