One group table (AUTO-509) (In progress) 

Having launch config, group config and group state in scaling_config table instead of 3 seperate tables. Also, when a group is created, a `created_at` column is added that is checked every time group or its related information is retrieved. This ensures that resurrected rows are not retrieved and are cleaned up. 

What is resurrected row you ask?  Sometimes (as described in https://issues.rax.io/browse/AUTO-509), the group is deleted but its state is updated before the delete gets propogated to all cass nodes. This creates a half filled incorrect group entry that actually should not be there. This is a resurrected row.

Note: This PR is not yet complete. The code is complete. Tests are on their way. However, reviewing it is greatly appreciated.