Code review comment for lp:~donal-lafferty/glance/fix739433

Donal, I took this branch and made changes to make the migration script Python-based, instead of just MySQL .sql migrate files. The reason is because we also needed PostgreSQL to migrate.

There is an issue with sa-migrate and SQLite, however, that produced an error in the sa-migrate workaround code for SQLite not having ALTER TABLE MODIFY COLUMN abilities. But, since SQLite doesn't have a concept of BIGINT, I simply made sure that the migrate script doesn't alter anything for SQLite engines.

Please merge lp:~jaypipes/glance/bug739433 into your branch locally and bzr commit && bzr push. While you do that, please do set this Merge Request to Work In Progress status, then back to Needs Review when you've pushed. Thanks for your patience on this.