pom.xml: update various versions

* Update killbill-api to 0.7.0 (new pagination API)
* Update killbill-plugin-api to 0.5.0 (new pagination API)
* Update killbill to 0.7.0 (new pagination JAX-RS API)
* Update killbill-analytics-plugin to 0.5.1

Signed-off-by: Pierre-Alexandre Meyer <pierre@mouraf.org>