Add a new Core Event launched when a repository initialization has completed

Some custom bundle developers might want to create an event listener triggered as soon as a Nuxeo Core repository has been initialized.

A typical use case would be to perform sanity checks on the existing document structure of the repository and create missing hierarchy elements when deemed necessary.

It would be great to make sure that this event is triggered whenever the repo is being re-initialized by the deployment of custom document types / schemas in a bundle managed by Nuxeo IDE upon hot-redeploy by the developer.