automatically requires adapters passed as string

I have the following problem:

I wrote a `manifest.json` where I configured dogwater like this:
```
    "dogwater": {
      "connections": {
        "diskDB": {
          "adapter": "disk"
        }
      },
      "adapters": {
        "disk": "sails-disk"
      },
      "models": [{
        "identity": "person",
        "connection": "diskDB",
        "attributes": {
          "name": "string"
        }
      }]
    }
```

This is extremely useful because I can then start my server using hapijs/rejoice without writing javascript code. Only configuring the system through a JSON file. This should be the hapijs approach.

Applying this patch I will be able to pass a string, which will be `required`, or choose to pass a complete object in there.

What do you think about it ?