Allow defining more than one model package in conf

exemple : module A use  modulea.models package name to store its OrientDB models, and module B use moduleb.models . Module C require module A and module B and contain the database settings in its application.conf.
With this change we can list package name (comma separated values) in application.conf

I set up a project example ( dumb wisdom-orientdb training) at this link :
https://github.com/remi-parain/wisdom-orientdb-training

Signed-off-by: Rémi Parain