WIP: Add atomic resource reservation to nodes.

Add explicit resource reservation to nodes.  To be used to handle port allocation amongst other things. 

Only updated a single types.go, since I expect some iteration here.  Will update all types when we reach consensus.
Do we view usage as part of `spec` or `status` according to v1beta3?  It seems more `status` like.  Capacity seems more `spec`, since an administrator can control how much of a host they wish to make available (although it could be automatically calculated).  Usage seems like it is always calculated, even if there is a component that is dependent on the state of other items in the system.