Add a virtual attribute provider that can be used to assign entryUUID values
for entries in private backends (e.g., the root DSE, schema, monitor entries,
config entries, etc.).  The entryUUID value that will be generated is based on
an MD5 hash of the entry DN, but this shouldn't be a problem for entries in
private backends because none of them allow modify DN operations.  User entries
should have a real entryUUID value generated when the entry is created (either
via an LDAP add or an LDIF import).

OpenDS Isssue Number:  1775