Add state management to quotas

Implement state management into Nova quotas such that they can be integrated into larger finance processes for public and private clouds. This way we could track not only the current quota total for a given tenant, but the history of the quota augmentations for each of those tenants. This means changing the quota model from per-tenant-per-resource to be a per-tenant-per-resource-per-request model. So the quota for a given tenant will actually be the sum of the /approved/ quota requests. Rather than whatever the current quota line is in the DB.