Add Branding model to subscriptions.
Complete branding db mappings for pool and subscription.
Update refresh pools for branding.
Import/export for branding.
Add brand name to cert, WIP.
use branding type from Branding, not product attrs

add new branding info to test data with OS in name
default to null when no branding exists
Merge pull request #545 from candlepin/dgoodwin/branding-round-2

Dgoodwin/branding round 2