This PR aims to add a production service for postgresql.

Changes:

• Update docker service for prostgresql in order to have it ready for production
• uses named volume for the postgresql data
• add scripts for restoring and dump

it resolves #105

Assumptions:

• In order to avoid any problems with the current postgresql server, it would be better to have a solution that would be easily switchable.
• using docker bind mount approach, it maybe could corrupt the current postgresql data folder on host in the setup (if something goes wrong)
• using docker bind mount approach, the backup would be easier
• using named volume approach, it is easy to switch to a cloud storage, or copy the entire volume to other containers, etc
• we can use the same strategy for staging and production and keep the production data safe

• bind mount, example: - /var/lib/postgresql/data/pgdata:/var/lib/postgresql/data/pgdata
• named volume, example: - pgdata:/var/lib/postgresql/data/pgdata