Improves provisioning scripts for different server roles

Previously all servers ran the same scripts and had the same setup. This
commit changes the scripts so that only the database server exposes a
postgres port, and only the web server installs nginx. This improves
security a little bit, but primarily just makes managing the servers
easier.
Correct user for ansible scripts
Adds instructions about handling GEOS issues in development on linux
Adds instructions on how to use ansible vault
Removes testing group var file
Correct ansible commands for provisioning

Stages now have separate inventory files so that they can be run
separately
Use correct inventory name for db config
Use correct psql flag for running commands non-interactively
Update ansible docs with correct host filenames
Update cleanup info in WDPA readme
Update servers provisioning docs after merging the ansible group vars
Merge pull request #50 from unepwcmc/ansible-db-servers

Ansible sets up DB servers correctly