1. Remove aliases from subcommands that change things (upgrade, downgrade,
revision, init) to reduce risk of accidental usage.
2. Add aliases to readonly subcommands (history, show, version,
dbversion)
3. Minor edits
Rationale: alternate config file applies to all subcommands, so, I
think, it is more correct to run this:
> ./db.sh -c mygalaxy.yml upgrade some-revision-id
than this:
> ./db.sh upgrade some-revision-id -c mygalaxy.yml
That's also consistent with how alembic handles this option.