Migration templates should use shared log

Migration templates currently use `console.log` in several places. It would be better to use the `db-migrate-shared` `log` functions, so that logging output can be controlled easily through global variables. In my case, I programmatically use `db-migrate` and prefer not to override the `console` functions.

Here is where `console.log` appears in the migration templates:

https://github.com/db-migrate/node-db-migrate/blob/688b89f0bd5d3729b28abf05c1002a089e13efd9/lib/migration.js#L159

https://github.com/db-migrate/node-db-migrate/blob/688b89f0bd5d3729b28abf05c1002a089e13efd9/lib/migration.js#L175

https://github.com/db-migrate/node-db-migrate/blob/688b89f0bd5d3729b28abf05c1002a089e13efd9/lib/migration.js#L223

https://github.com/db-migrate/node-db-migrate/blob/688b89f0bd5d3729b28abf05c1002a089e13efd9/lib/migration.js#L244
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