[YUNIKORN-632]Add apache headers to generated files (#36)

Add Apache license headers to GENERATED_HEADER area which located on Makefile.
So the generated files will include the license when we generate those files.
diff --git a/Makefile b/Makefile
index a708501..28ec633 100644
--- a/Makefile
+++ b/Makefile
@@ -55,6 +55,21 @@
 INTERFACE_GO := $(API_LIB)/interface.go
 
 define GENERATED_HEADER
+/*
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you 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.
+*/
 
 // Code generated by make build. DO NOT EDIT
 
diff --git a/lib/go/api/interface.go b/lib/go/api/interface.go
index caacb1d..02494b7 100644
--- a/lib/go/api/interface.go
+++ b/lib/go/api/interface.go
@@ -1,3 +1,18 @@
+/*
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you 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.
+*/
 
 // Code generated by make build. DO NOT EDIT
 
diff --git a/lib/go/common/constants.go b/lib/go/common/constants.go
index 4b032ba..da1ebd2 100644
--- a/lib/go/common/constants.go
+++ b/lib/go/common/constants.go
@@ -1,3 +1,18 @@
+/*
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you 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.
+*/
 
 // Code generated by make build. DO NOT EDIT
 
diff --git a/si.proto b/si.proto
index b0cebab..f4b8c22 100644
--- a/si.proto
+++ b/si.proto
@@ -1,3 +1,18 @@
+/*
+ Licensed to the Apache Software Foundation (ASF) under one
+ or more contributor license agreements.  See the NOTICE file
+ distributed with this work for additional information
+ regarding copyright ownership.  The ASF licenses this file
+ to you 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.
+*/
 
 // Code generated by make build. DO NOT EDIT