Generate javadoc for gerrit extension and plugin API

To make the consumption of the gerrit extension and plugin API easier
for plugin developers gerrit-extension-api.jar and
gerrit-plugin-api.jar should be published to Maven central. For this
having javadocs generated is required.

Change-Id: Ibb13fbb61c94c76fe6e2f7041d5a1e269d39d788
Signed-off-by: Edwin Kempin <edwin.kempin@sap.com>
4 files changed