Fix deleteFile (missing deletes for etcd metadata)

Also move resource and serializer interfaces to types.go

controller/types.go

@@ -0,0 +1,28 @@
+/*
+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 controller
+
+type (
+	resource interface {
+		Key() string
+	}
+
+	serializer interface {
+		serialize(r resource) ([]byte, error)
+		deserialize(buf []byte, r resource) error
+	}
+)