Also make the output and validation of input better for kubecfg api calls.
Kubecfg will now display a usage argument if the URL is incorrect or an
unrecognized storage type is passed.
Check for 1 path segment on create/list, 2 on update/delete, and
allow any number of path segments on get (for now).
Also pretty prints the list of actual types that are supported for
create/update, which today corresponds to the list of types that
are supported period.
