Add a dbdump to the migration process to allow rollbacks of schema changes

[jeremy-moffitt]

In order to support the ability to rollback schema changes, a copy of the database should be created prior to performing a migration. This should be automatic.

Acceptance Criteria:

1. Migrations automatically create a dbdump prior to migration
2. Create a set of instructions for rolling back the database using the dbdump

[jeremy-moffitt]

Note that in the short term this is a manual task and there is agreement that that is an acceptable solution for now given the infrequency of schema updates.