Apply header changes from doco

See https://www.eclipse.org/legal/epl-2.0/faq.php#epl-relicensing

license-header-epl2.txt

@@ -1,8 +1,10 @@
 Copyright (c) ${year} Sonatype, Inc.
 All rights reserved. This program and the accompanying materials
-are made available under the terms of the Eclipse Public License v2.0
+are made available under the terms of the Eclipse Public License 2.0
 which accompanies this distribution, and is available at
 https://www.eclipse.org/legal/epl-2.0/
 
+SPDX-License-Identifier: EPL-2.0
+
 Contributors:
   Stuart McCulloch (Sonatype, Inc.) - initial API and implementation