Allow datacontext to return the real values for concepts and filters

![screen shot 2014-05-29 at 11 06 52 am](https://cloud.githubusercontent.com/assets/2774472/3119075/eb405cf4-e742-11e3-936a-7edb45d6961d.png)

What is returned when a filter is applied.

This will be used to apply styles to the filter display in filter.js 

Signed-off-by: Sheik Hassan <solergiga@yahoo.com>
The final `else` needs to be added for a single non-model value:

```python
if value in value_labels:
    label = value_labels[value]
else:
    label = smart_unicode(value)

cleaned = {
    'value': value,
    'label': label,
}
```

The final block would handle `QuerySet` and `Model` instances (key-based), and list/tuples and values (primitive values).