allow modify labels/annotations of copied resources

[profiprog]

This is solution for issues #509 and #465 Is adding new annotations kubed.appscode.com/sync-labels and kubed.appscode.com/sync-annotations which can be added to source resource...

...
  annotations:
    kubed.appscode.com/sync: copy-this-resource=true

    # label `app.kubernetes.io/instance` will be removed in target resource because doesn't specify any value
    # label  `managed-by` will be created or replaced in target resource by value 'author'
    kubed.appscode.com/sync-labels: |
      app.kubernetes.io/instance
      managed-by=author

    # same logic but applied for target annotations
    kubed.appscode.com/sync-annotations:
...