Add script to add "centroid" column to locations.

This script is just part of the process of fill
all centroid columns with computed values from
`compute_centroids.py`
Add centroid attribute to Location Model
Add script to check centroid computed value
Save computed centroid attribute
Remove all polygon/shape related code.

* Project view
* Investment view
Merge pull request #13 from ecofunds/feature/add_location_centroid

Feature/add location centroid