Publication: have different publishing behaviour

Implement which behaviour to adopt when the target space is already populated:

• "Cancel" for not publishing (do not start the job, also may be blocked before in the preview from BVERSION-81)

• "Update" to publish update existing pages, add new pages from source but leave page deleted from source in the destination. Pages marked as deleted in source will be removed from destination.
• "Re-publish" to reset the destination space.

Currently, the behaviour is an "update" without removing pages marked as deleted.

Once the implementation is done, remove the property name "publishBehaviour" from disabledProperties in PublicationConfigurationSheet, in order to display it and make it available to the user.