DS-2081: Delete EPersons even if submitted Items or are refrenced elsewhere in DSpace

Do NOT merge this PR it needs further testing.

The code is not well tested yet. It may interfere with the metadata for all DSOs contribution. I want to add some unit tests. I'm out of office till October 15 and will clean this PR as soon as I'm back. I asked peterdietz and hpottinger and they are willing to include it in DSpace 5 if this PR is complete and merged prior to the "feature freeze" deadline of October 20, 2014.