Rationalize use of namespace/name.

Address @thockin comment from #1297 about namespace/name being consistent across objects, resources, and labels.

Confined k8s resources to have names which are DNS_SUBDOMAIN format, rather that path.  Since we only have two resources so far, it seemed safe to restrict this space a bit.  FYI @johnwilkes 
 
Also added text to labels doc describing their format.  FYI @bgrant0607 

Also FYI @derekwaynecarr 
Regarding lavalamp's comment:
I've filed an issue about how to deal with namespaces and labels.  I've changed this text to refer to that issue. 

Regarding johnwilkes's comment about DNS_LABEL.
The point of this PR was to have consistency across REST object, label and resource (base) names.  This was suggested by Tim.  Tim to decide if we still want this or not.