should get informed which of the 2 namespaces could not be deleted

[adietish]

follows up on #136 (PR #137)

Steps:

1. ASSERT: have a namespace that you created and that you can delete without harm (ex "test")
2. ASSERT: have the namespace "kube-system" (which is present in every kubernetes-cluster, visible if you're admin. It cannot be deleted)
3. EXEC: select both and pick "Delete" in the context

Result: You're informed that both namespaces could not be deleted. In reality, only "kube-system" could not be deleted, "test" has been deleted. There's actually no harm in this erroneous reporting. The namespace "test" disappears" as soon as it is removed by the cluster.

[adietish]

Of course the resources that succeeded should additionally be notified in an information notification as noted in #148