Add models directory for old generators

[DesignByOnyx]

This has been a long time coming. Closes #94

I did some pretty extensive testing and I think this sets us up to have more configurable db options in the future.

[daffl]

This looks great, thank you! Dang, if I'd known I would've suggested to make those changes against the /~https://github.com/feathersjs/generator-feathers/tree/generator-refactoring branch (also see PR #159). It has some pretty extensive changes but is there any chance we can port this setup to that branch?

[DesignByOnyx]

I almost finished making the changes against the new generators last night. There's a little more complexity to it, but I really like the updates.

[daffl]

This has been superseded by #162. Thanks again!