Feature/add location centroid

## Investment Map View

```sh
python misc/request.py http://localhost:8000/ajax/investment/mapsource/?view=density&zoom=6

Testing localhost:8000...

Response 0.0312588214874
Response 0.0342879295349
```

## Project Map View

```sh
python misc/request.py http://localhost:8000/ajax/project/mapsource/?page=&list_type=1&order_by=&s_project_name=&s_all_project_name=0&s_project_activity_type=&s_all_project_activity_type=0&s_country=&s_state=&s_organization=&s_all_organizations=0&s_investments_from=&s_investments_to=&s_date_from=&s_date_to=&view=heat&chart=false&chartType=bars

Testing localhost:8000...

Response 0.0644221305847
Response 0.0302679538727
```