Dynamic Volume Provisioning

[MaxFedotov]

This PR closes #56 and adds support for Dynamic Volume Provisioning feature.

It implements 2 methods for Controller service - CreateVolume and DeleteVolume.
As CreateVolume don't provide an ability to specify an image, which will be passed to volumeHandle field in PersistentVolume object, a custom csi.storage.k8s.io/image annotation for PersistentVolumeClaim is used to store it:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  annotations:
    csi.storage.k8s.io/image: docker.io/warmmetal/csi-image-test:check-fs
  name: image-pvc
  namespace: system-driver-image-csi
spec:
  accessModes:
  - ReadOnlyMany
  resources:
    requests:
      storage: 6Gi
  storageClassName: system-image
  volumeMode: Filesystem

Also, CreateVolumeRequest is lacking information about annotations set on PersistentVolumeClaim (see kubernetes-csi/external-provisioner#86), so a custom watcher is implemented, which watches and indexes PersistentVolumeClaim and is used to get this annotation value.

PR also includes Helm chart refactoring, so it complies with Recommended mechanism for deploying csi drivers.