Add Ldaptive support for Relay staff attributes

@frett 

Note this PR already includes the changes from https://github.com/GlobalTechnology/idm-user-management/pull/6
ok, that makes more sense then.

I would still like to see cruPerson change to an Auxiliary objectClass for the merge, as it stands it can't be added/removed for existing objects in eDirectory because it is currently a structural objectClass. This would need to be updated in iManager though, not something captured in this code.