@default tag: added support for object literal defaults

Some fields contain objects as their default value. They are now stored as a string and, in the default template, displayed with syntax highlighting.

```javascript
/**
    @default
 */
var obj = { value_a : 'a', value_b : 'b' };
```

Becomes

![object default 2](https://f.cloud.github.com/assets/1655575/482760/6596cc94-b8a6-11e2-86e1-2822bd8ac71b.png)

The code is covered by a unit test.

The CSS was changed to not have the highlighted code disrupt the border next to the field details.