Add namespaces endpoint

This is being added because multiple namespaces can now be used
on Kubernetes. By listing namespaces, a client such as the UI
or CLI can then enumerate the namespaces to find functions
which may span across more than one namespace.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

gateway/vendor/github.com/openfaas/faas-provider/types/config.go

@@ -7,11 +7,13 @@ import (
 
 // FaaSHandlers provide handlers for OpenFaaS
 type FaaSHandlers struct {
-	FunctionReader http.HandlerFunc
-	DeployHandler  http.HandlerFunc
 	// FunctionProxy provides the function invocation proxy logic.  Use proxy.NewHandlerFunc to
 	// use the standard OpenFaaS proxy implementation or provide completely custom proxy logic.
-	FunctionProxy  http.HandlerFunc
+	FunctionProxy http.HandlerFunc
+
+	FunctionReader http.HandlerFunc
+	DeployHandler  http.HandlerFunc
+
 	DeleteHandler  http.HandlerFunc
 	ReplicaReader  http.HandlerFunc
 	ReplicaUpdater http.HandlerFunc
@@ -19,10 +21,11 @@ type FaaSHandlers struct {
 	// LogHandler provides streaming json logs of functions
 	LogHandler http.HandlerFunc
 
-	// Optional: Update an existing function
-	UpdateHandler http.HandlerFunc
-	HealthHandler http.HandlerFunc
-	InfoHandler   http.HandlerFunc
+	// UpdateHandler an existing function/service
+	UpdateHandler        http.HandlerFunc
+	HealthHandler        http.HandlerFunc
+	InfoHandler          http.HandlerFunc
+	ListNamespaceHandler http.HandlerFunc
 }
 
 // FaaSConfig set config for HTTP handlers