Skip "--host" parameter when creating / dropping databases / users on localhost because otherwise user gets asked for a password on Ubuntu and thus the Vagrant test fails
Improve formatting
Fix typo
Replace the fancy "IF EXISTS" query with a simple "CREATE USER" + error message checking because Ubuntu's Bash behaves differently with variables that contain "$"
Confirm removal of PostgreSQL databases and users while also listing what exactly will be removed; the "purge_mediacloud_databases.sh" script is now smart enough to read the database credentials from "mediawords.yml" so this is an additional measure to prevent deletion of production databases