Add pluginRepositories section to help resolving Maven plugins

Add pluginRepositories section to help resolving Maven plugins

<pluginRepositories> are used to determine where to download plugins
used by Maven in order to build. While <repositories> is used to
download artifacts depended by a project during a build. We need both
defined in order to successfully download all artifacts using the
OpenDaylight mirror and not relying on Maven Central directly.

- Add pluginRepositories section to help resolve Maven plugins
- Change tab setting to 2 for xml
- Update Copyright year

Change-Id: I5ad09d6337d4f27768cd9f4af185018e0f91f7b8
Signed-off-by: Thanh Ha <thanh.ha@linuxfoundation.org>