Use schema migration tools to create SQL Tables

[diptanu]

Use a schema migration tool to create, drop and alter tables. Currently it's being done by -

1. Raw SQL files contain the commands to create the schema from command line using mysql and psql clients.
2. The unit test setup reads these files and runs them in setup.

Some possible schema migration tools to explore -

1. dbmate
2. flywaydb

A tool which doesn't require a lot of dependencies are preferred to simplify deployment and operations for users.