[PD-829] Script to update onet <-> moc mappings

* Got rid of the update_locations.py script since we don't need it any more (was an artifact of introducing multiple locations to PRM)
* created one-off script that when imported and its run function is called, will parse a csv file and update the Onet, Moc, and MocDetail tables.

Should I try and find the other onet updating script and seeing whats generalizable between those and this? The idea would be to have a manage.py command that will allow us to do this on an infrequent basis:
```
python manage.py update_onets cool.csv --moc_title "Title" --moc_code "Code"
```
Or something like that. If not, I'm fine with this staying as a one-off.