feat: Add Postgresql Migrations

[jameshclrk]

- Summary Fixes #176

This adds postgresql migrations so that gotrue can do the migrations.

MySQL migrations are renamed to have .mysql. so they are picked when mysql is the driver.

This uses the built in feature of pop/soda.

- Test plan I have tested this locally, but if someone else would have a look that would be great.

- Description for the changelog Add Postgresql versions of the migrations

[paulftw]

@netlify-team-account-1 any chance this will get merged any time soon?