Migration Config format is incorrect

[davesag]

Currently we are emitting an object with format

{
  database,
  username,
  password,
  dialect,
  operatorsAliases,
  logging,
  options
  }

But according to https://github.com/sequelize/cli/blob/master/src/helpers/config-helper.js#L67

it ought to be

{
  database,
  username,
  password,
  dialect,
  host,
  port,
  operatorsAliases
}

The operatorAliases, logging and options are not needed for running migrations, and the host and port need to be top-level values, not injected into the options.