Use the collector namespace for graphite host and port.

Enables one to have 

```
properties:
  collector:
    use_graphite: true
    graphite:
      address: 10.220.0.234
      port: 2003
```

instead of

```
properties:
  collector:
    use_graphite: true

  graphite:
    address: 10.220.0.234
    port: 2003
```

in the manifest.