Add language pack dashboard

Front-end for lang pack dashboard, looks like:
![selection_069](https://cloud.githubusercontent.com/assets/1319950/4211174/4d473ed6-3883-11e4-9c52-ea84c6e3d532.png)

Note: 

This depends on a templatetag I wrote and included in fle_utils. @aronasorman let me know what you want to do about that.... Could include it as a central only templatetag to make this a simpler integration, but I could see it being useful for coachreports on distributed. 

```python
@register.filter
def compute_percent(numerator, denominator, precision=1):
    if not numerator or not denominator:
        return None
    return floatformat((float(numerator) / float(denominator)) * 100, precision) + '%'
```
Please wrap this in a `with` statement for the file to be closed right after it's used. We don't want any dangling file handles!