Namespace aws datadog and tsdb

Hello, just making config of collector a little bit nicer(to my mind).

```
--- 
properties: 
  collector: 
    use_aws_cloudwatch: true
    aws: 
      access_key_id: 
      secret_access_key: 

    use_datadog: true
    datadog: 
      api_key: 
      application_key: 

    use_graphite: true
    graphite: 
      address:
      port:

    use_tsdb: true
    opentsdb: 
      address: 
      port: 
```

Instead of 

```
--- 
properties: 
  collector: 
    use_aws_cloudwatch: true
    aws_access_key_id: 
    aws_secret_access_key: 

    use_datadog: true
    datadog_api_key: 
    datadog_application_key: 

    use_graphite: true
    graphite: 
      address:
      port:

    use_tsdb: true

  opentsdb:  <= Notice how its not under collector :(
    address: 
    port: