Pictures

Shows pictures in the detail view.

* Takes pictures from the Durham County Tax DB and shows them in the detail view for each establishment.
* Mapping restaurant <-> property_id has to be imported from the new cvs file in ```Durham-Data``` using:
```python manage.py importer```
It only has to be run one time.
* Input field below the picture allows manual modification of the property_id in case of mistakes (TODO: has to be removed for production).
* Also fixes #30