pom.xml: add various dependencies from killbill-server

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
pom.xml: configure maven-jar-plugin

Add <skipIfEmpty>true</skipIfEmpty> in the configuration section (see
http://jira.codehaus.org/browse/MJAR-139).

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
pom.xml: add jetty-console-maven-plugin

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
pom.xml: fix styling

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>
pom.xml: ignore .bak files for rat

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>