Expand file fields

Instead of file fields returning as:

    "image": "{filedir_1}image_name.jpg"

They are now returned as:

```
"image": {
    "file_id": "120",
    "site_id": "1",
    "title": "image_name.jpg",
    "upload_location_id": "1",
    "rel_path": "/images/uploads/main_images/image_name.jpg",
    "mime_type": "image/jpeg",
    "file_name": "image_name.jpg",
    "file_size": "1672632",
    "description": null,
    "credit": null,
    "location": null,
    "uploaded_by_member_id": "1",
    "upload_date": "1382604425",
    "modified_by_member_id": "1",
    "modified_date": "1382604425",
    "file_hw_original": "1728 2304",
    "raw_output": "{filedir_1}image_name.jpg",
    "path": "http://domain.dev/images/uploads/main_images/",
    "extension": "jpg",
    "filename": "image_name",
    "url": "http://domain.dev/images/uploads/main_images/image_name.jpg",
    "width": "2304",
    "height": "1728",
    "image_pre_format": "",
    "image_post_format": "",
    "file_pre_format": "",
    "file_post_format": "",
    "image_properties": "",
    "file_properties": "",
    "url:list": "http://domain.dev/images/uploads/main_images/_list/image_name.jpg",
    "url:slide": "http://domain.dev/images/uploads/main_images/_slide/image_name.jpg",
    "url:hero": "http://domain.dev/images/uploads/main_images/_hero/image_name.jpg"
}
```

Sorry about all the whitespace diffs btw - Got ST2 to auto-trim it all on save by default. Feel free to close this PR and add the changes into your branch instead if you like.