teststep apply, assert and errors can now take urls, files or folder

[kensipe]

TestStep Apply, Errors and Asserts can now have urls (in addition to folders and files)

apiVersion: kudo.dev/v1beta1
kind: TestStep
apply:
  - https://mesosphere.github.io/kubeaddons/bundle.yaml

Is completely legit now.

There was an interesting situation with the kubeaddons url as well. It has a file headers of:

# DO NOT EDIT: this file is generated

---
apiVersion: apiextensions.k8s.io/v1beta1

The 3 lines prior to the separator creates an unstructured object (without an error) but isn't valid. This need detection has been added to the code as well.

Signed-off-by: Ken Sipe kensipe@gmail.com

Fixes #114

[kensipe]

As a side note: it would be great to do this with manifests as well.. however today it is called manifestsDir... I think it would be best to switch to the new structure in KEP06 before adding url as an option. We should call it manifests:

[ANeumann82]

tbh, I'm not sure if it's a good idea that people use external files for apply/assert/error, but... They'll do it anyway :)

The PR itself lgtm

[zmalik]

LGTM!