Do not wipe database in production

[morenoh149]

If the DATABASE_URL env var is defined we act like we are in production. When we are in production we wipe the db if the api restarts.

1. env var DATABASE_URL should not imply production
2. do not wipe db if we are in production
3. factor out the seeding step into a separate file while we are at it.

Relevant code https://github.com/the-road-to-graphql/fullstack-apollo-express-postgresql-boilerplate/blob/master/src/index.js#L94

[rwieruch]

Related https://github.com/the-road-to-graphql/fullstack-apollo-express-postgresql-boilerplate/pull/54