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 
I find this very confusing. This text makes it sound like labels are part of the kubernetes object namespacing system. I would have expected that the purpose of adding namespaces to labels is to prevent naming collisions, in which case they are segmenting "label name namespace" and not "kubernetes object namespace". Do I misunderstand this?