Make the trunk studio jar available though the maven repository

Currently it is not possible to put the dev version of the configuration in continuous integration: only tagged versions are retrieved.
Other improvements should be done: the pom file is generated for any given version, it should return a 404 when version does not exist. This pom file could also contain a dependency to the target nuxeo-distribution-dm version.
Ideally a listing of existing versions would be also a good thing.