Add "internal" routes for all functions

These routes allow us to call any function without explicitly defining
a route for them.  TODO: if we can serve these routes from a separate
instance of router (controlled by a commandline flag or env var), we'd
be able to keep this instance of the router "private" by not assigning
it a loadbalancer/nodeport or other externally-visible service.

common.go

@@ -0,0 +1,25 @@
+/*
+Copyright 2016 The Fission Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package fission
+
+import (
+	"fmt"
+)
+
+func UrlForFunction(m *Metadata) string {
+	return fmt.Sprintf("/fission-function/%v/%v", m.Name, m.Uid)
+}