Fix kubectl get -f <file> -o <nondefault printer> so it prints all the
objects in the file, instead of just the first one. Also add a test for
this feature.
Switch to allowing missing keys in jsonpath templates by default.
Add support for allowing/disallowing missing keys in go templates
(default=allow).
Add --allow-missing-template-keys flag to control this behavior
(default=true / allow missing keys).