add namespace param for fn and env (#2556)

This PR moves fission CLI as closer as possible to kubectl command behaviour.  We have improved namespace handling behaviour across CLI.

* add namespace param for fn and env
* use common fn for ns check
* update validation
* default namespace for httpTrigger, env and package, config and triggers
* use default ns
* add namespace filter to spec
* add forceNamespace flag
* set current namespace
* add default namespace in config
* add namespace specific destroy
* add all namespace in the list of resources
* add namespace as global tag
* use %s instead of %v
* add test cases for namespace
* use ns in get all functions

pkg/fission-cli/cmd/mqtrigger/delete.go

@@ -45,10 +45,16 @@ func (opts *DeleteSubCommand) do(input cli.Input) error {
 	return opts.run(input)
 }
 
-func (opts *DeleteSubCommand) complete(input cli.Input) error {
+func (opts *DeleteSubCommand) complete(input cli.Input) (err error) {
+
+	_, namespace, err := util.GetResourceNamespace(input, flagkey.NamespaceTrigger)
+	if err != nil {
+		return errors.Wrap(err, "error in deleting function ")
+	}
+
 	opts.metadata = &metav1.ObjectMeta{
 		Name:      input.String(flagkey.MqtName),
-		Namespace: input.String(flagkey.NamespaceTrigger),
+		Namespace: namespace,
 	}
 	return nil
 }