Added postgres DB import/export for local development copy and added localhost functionality into db.php

see https://github.com/khbites/wordpress-heroku-lgl#postgres-database-syncing (i.e. README.md) for the extended doc 

db.php has an added filter function to return localhost for home and siteurl, so you don't need to change this inside the db for wordpress. If you don't do this and you go to http://localhost/wp-admin you get the login screen put the post gets sent to your production server (siteurl). With this little filter function a DB dump from your production server works on your local copy without any changes.