Move the internal minion representation to match v1beta3

@ddysher review please, this includes removing the duplicate Labels

Extracted from #1600
@bgrant0607 interpreting your comment on the other pull, I moved Capacity to NodeSpec (I specify what capacity this node has), and when we introduce "Available" I assume it would be on NodeStatus.  I kept NodeResources for now as a generic container to support CloudProvider, but I'm not sure we wouldn't just remove it in the future and use Capacity and "Whatever".  Let me know if this is not the direction you intended.