Add pom with meta-data for plugin projects

These pom files are needed to be able to upload the plugin artifacts
to Maven Central.

Change-Id: I7c812538a4c2ddf684c0b6696fb7efc0a42002e4
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
Merge "Add pom with meta-data for plugin projects" into stable-2.9