Rename Minions -> Nodes internally

Allows "minions" to be passed to v1beta3, and "nodes" to be passed to v1beta1/v1beta2 
endpoints. Relaxes conversion type checking on names where conversion is possible.

Now the API will respond to:

    /api/v1beta1/nodes
    /api/v1beta2/nodes

identically to their "minions" counterparts.  Kubectl and kubecfg will also respect
"nodes".  

A few other little fixes in the change.  The big one is the mechanical find and replace.

Addresses parts of #1519