Sets the task as multitask

So it'll support:

```
configureRewriteRules: {
  app: {
    options: {
      rulesProvider: 'connect.app.rules'
    }
  },
  "static": {
    options: {
      rulesProvider: 'connect.static.rules'
    }
  }
}
```
then the tasks will be `configureRewriteRules:app` and `configureRewriteRules:static`