Summary:
as defined in KEP-0017 we introduce a new Pipe task. Given a task specification like:
```
tasks:
  - name: genfiles
    kind: Pipe
    spec:
      container: container.yaml
      pipe:
        - file: /tmp/foo.txt
          kind: Secret # or ConfigMap
          key: foo
```
KUDO will:
- create a Pod with the provided `container.yaml`
- wait for successful execution of the container
- copy out specified pipe files
- store them in the API server (in the above example as a Secret)
- the secret can be referenced in the subsequent resources as `{{Pipes.foo}}`

For more information about the implementation please consult the KEP-0017.

Fixes: #774

additionally, instance controller doesn't not reconcile on pipe-pod deletion events

and with them goroutines and a lot of complexity.

additionally PodExec caller can now differentiate between command execution failures (exit code > 0) and other errors