Add environment variable for (dev) postgresql host
Add environment variable for (dev) postgresql host

This falls back to localhost so it won't break any existing
configuration.

karuppiah7890/Mail-for-Good,zhakkarn/Mail-for-Good,zhakkarn/Mail-for-Good,karuppiah7890/Mail-for-Good,zhakkarn/Mail-for-Good,karuppiah7890/Mail-for-Good