Update the createEntry method to be more intelligent about the structural
objectclass that it uses for the entry that gets created.  If the DN contains a
single RDN attribute, then the following mappings will be used:

- c             -> country
- dc            -> domain
- o             -> organization
- ou            -> organizationalUnit
- anything else -> untypedObject

If the RDN contains multiple attributes, then the untypedObject class will
always be used.  If any of the RDN attributes are not allowed by the
untypedObject class, then extensibleObject will also be included.