Add coflict handling for persons

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Better conflict resolving in PersonAdmin

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Add migration to remove person uniqueness check

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Resolve conflicts only for newly added persons

Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>