license header for scala files

src/main/scala/eu/nomad_lab/normalizers/RepoTagsNormalizer.scala

+/*
+   Copyright 2016-2017 The NOMAD Developers Group
+
+   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 eu.nomad_lab.normalizers
 
 import eu.{ nomad_lab => lab }