Rename prod directory

We had a conflict in that `deploy prod` was not working because we had an existing directory prod in our project. We had to resort to rename the deploy target to prd.

This PR renames the directory `prod` to `prd` to be able to use `deploy prod` which is more consistent with all our other projects deploy process.

Please note the following:
- The URL for production is still `http://.../../prod`
- Make target and test targets are still named prod
- Once this in master, you have to delete the existing prod directory by hand
- After make, you have to restart apache to take care of the new configuration

I'll recommend to merge this soon and then rebase your open branches (otherwise you'll have to do the above steps repeatedly)