Move type LabelSelector and type LabelSelectorRequirement from pkg/apis/extensions
This avoids an import loop when Job (and later DaemonSet, Deployment, ReplicaSet)
are moved out of extensions to new api groups.
Also Move LabelSelectorAsSelector utility from pkg/apis/extensions/ to pkg/api/unversioned/
Also its test.
Also LabelSelectorOp* constants.
Also the pkg/apis/extensions/validation functions ValidateLabelSelectorRequirement and
ValidateLabelSelector move to pkg/api/unversioned
The related type in pkg/apis/extensions/v1beta1/ is staying there. I might move
it in another PR if neccessary.
Combine the fields that will be used for content transformation
(content-type, codec, and group version) into a single struct in client,
and then pass that struct into the rest client and request. Set the
content-type when sending requests to the server, and accept the content
type as primary.
Will form the foundation for content-negotiation via the client.
