WIP - a Per-Node controller

    This is a sketch of a controller that runs a pod on every node.
    
    Issues:
    
    Adding a new REST resource is incredibly tedious.  We should make REST
    plugin-able and make them all completely self-contained plugins.
    
    This being the first controller that isn't replication, lots of words are
    wrong all over.  We've taken a lot of shortcuts and called
    ReplicationControllers "controllers" all over.  E.g. the etcd path.
    
    Do we want this to be a "sub-kind" of replication controller?  Or do we want
    a new top-level REST object?
    
    Kubectl should be able to load some form of plugin that allows for
    descriptions and formatting without rebuilding.

@ddysher note overlap with node manager.