Portworx Volume Driver in Kubernetes

- Add a new type PortworxVolumeSource
- Implement the kubernetes volume plugin for Portworx Volumes under pkg/volume/portworx
- The Portworx Volume Driver uses the libopenstorage/openstorage specifications and apis for volume operations.

Changes for k8s configuration and examples for portworx volumes.

- Add PortworxVolume hooks in kubectl, kube-controller-manager and validation.
- Add a README for PortworxVolume usage as PVs, PVCs and StorageClass.
- Add example spec files

Handle code review comments.

- Modified READMEs to incorporate to suggestions.
- Add a test for ReadWriteMany access mode.
- Use util.UnmountPath in TearDown.
- Add ReadOnly flag to PortworxVolumeSource
- Use hostname:port instead of unix sockets
- Delete the mount dir in TearDown.
- Fix link issue in persistentvolumes README
- In unit test check for mountpath after Setup is done.
- Add PVC Claim Name as a Portworx Volume Label

Generated code and documentation.
- Updated swagger spec
- Updated api-reference docs
- Updated generated code under pkg/api/v1

Godeps update for Portworx Volume Driver
- Adds github.com/libopenstorage/openstorage
- Adds go.pedge.io/pb/go/google/protobuf
- Updates Godep Licenses

cmd/kubelet/app/plugins.go

@@ -46,6 +46,7 @@ import (
 	"k8s.io/kubernetes/pkg/volume/iscsi"
 	"k8s.io/kubernetes/pkg/volume/nfs"
 	"k8s.io/kubernetes/pkg/volume/photon_pd"
+	"k8s.io/kubernetes/pkg/volume/portworx"
 	"k8s.io/kubernetes/pkg/volume/projected"
 	"k8s.io/kubernetes/pkg/volume/quobyte"
 	"k8s.io/kubernetes/pkg/volume/rbd"
@@ -90,6 +91,7 @@ func ProbeVolumePlugins(pluginDir string) []volume.VolumePlugin {
 	allPlugins = append(allPlugins, azure_dd.ProbeVolumePlugins()...)
 	allPlugins = append(allPlugins, photon_pd.ProbeVolumePlugins()...)
 	allPlugins = append(allPlugins, projected.ProbeVolumePlugins()...)
+	allPlugins = append(allPlugins, portworx.ProbeVolumePlugins()...)
 	return allPlugins
 }