fix for #1077
Update formatNamedParameters to not match parameters starting with digit

Using a query like:
query = "SELECT * FROM t WHERE create_at > CURRENT_DATE + CURRENT_TIME - time '01:30' LIMIT :limit";
Sequelize.query(query, null, {raw: true}, { limit: limit })
will fail due to "time '01:30'" where it will look for a parameter named '30'
added a test
Make available migrator helpers

This has been done so other tools can interact with the current migration state and more advanced tooling for migrating.
updated the test for postgres
Merge pull request #1086 from triptec/master

Update formatNamedParameters to not match parameters starting with digit
Merge pull request #1087 from webcast-io/feature/export-migrator-helpers

Make available migrator helpers