Enable public IPs even in not createExternal...

This allows the proxier to portal Public IPs even if the
createExternalLoadBalancer flag is not set.

This also fixes what appears to be a bug in the createExternalLoadBalancer path
wherein multiple PublicIPs would get truncated.
Support remote docker hosts on OS X.

This commit brings two main changes, notably:

Two new options that can be set as environment variables

- DOCKER_OPTS: any arbitrary set of docker options. Example: --tlsverify
- DOCKER_NATIVE: This forces the use of the native docker available.
                 This is most useful if you're on OS X and do not want
                 to use boot2docker.

Now uses 'docker cp' instead of tar piping to transfer files. This
currently must be done by copying the binaries off of the docker volume
and into a local filesystem (/tmp) before a docker cp is done. This
workaround will no longer be necessary after bug fix
https://github.com/docker/docker/pull/8509 makes it into stable.

This was necessary because the tar | tar method was creating corrupted
archives on OS X even with the < /dev/null workaround.
Make credentialprovider less verbose about benign errors.

In particular, a few of the utilities used within the credentialprovider had the pattern:
   glog.Errorf("while blah %s: %v", s, err)
   return nil, err

This change propagates those error message and puts the burden of logging on the caller.

In particular, this allows us to squelch all output during kubelet startup when we are detecting whether certain credentialprovider plugins should even be enabled.

Fixes: https://github.com/GoogleCloudPlatform/kubernetes/issues/2673
clean up error message on labels validation errs
Add namespacing for label keys
Loosen DNS 952 for labels
Merge pull request #2692 from jameskyle/develop

Support remote docker hosts on OS X.
Merge pull request #2635 from thockin/public-ip

Enable public IPs even in not createExternal...
Refactor kubelet, standalone k8s and integration test to all use the same code.
Add a test for important URLs.
Kubernetes version v0.6.0-dev
Kubernetes version v0.6.0
Merge pull request #2698 from brendandburns/release

Release 0.6.0
Relax search criteria to find both pod & bound pod events
Document API doc path.
Merge pull request #2689 from brendandburns/standalone

Refactor kubelet, standalone k8s and integration test to all use the same code.
Fix a logic error in the events e2e test.
Adding an e2e test for monitoring.
Update exec health check message logged

Update message logged after performing exec health check per #2708.
Remove empty lines when file is generated from jinja template