Facia tool: trailtext and image controls


Trailtext and image controls are available on all first-level items (ie. not on supporting content). 

![fronts-tool](https://f.cloud.github.com/assets/1147913/1853032/4871beee-7705-11e3-8d87-477fb4edc1de.png)

The highlighted item uses all the possible overrides, producing the following json: 

```
{
    "id" : "uk-news/2014/jan/06/flood-warnings-continue-rain-storms",
    "meta" : {
      "trailText" : "Environment secretary accused of 'buck passing', while vast waves and strong winds batter coast",
      "headline" : "Flood warnings continue as UK hit by more storms",
      "supporting" : [ {
        "id" : "news/2014/jan/06/best-pictures-of-the-day-live",
        "meta" : {
          "headline" : "In pictures"
        }
      }, {
        "id" : "environment/2014/jan/06/britain-wild-weather-rain-storms-floods",
        "meta" : {
          "headline" : "Britain's wild weather"
        }
      } ],
      "imageTone" : "hide",
      "group" : "0"
    }
  }
```