This plugin module was left out during Buck migration.
$>buck build api
produces now plugin-gwtui.jar and plugin-gwtui-src.jar.
Buck Maven bridge was enhanced to {install|deploy} the new artifact to
remote or local Maven repositories:
$>buck build install_api
deployes
gerrit-plugin-gwtui-2.9-SNAPSHOT-sources.jar
gerrit-plugin-gwtui-2.9-SNAPSHOT.jar
to local Maven repository.
Change-Id: Idae18f6df2e67fe53d57b8c35caa4226333e269b
c8cffc8e92