This method will instantly carry out an update() after the
move, so the entry is moved instantly.
You can pass an optional Horde_Ldap object. In this case, a
cross directory move will be performed which deletes the entry
in the source (THIS) directory and adds it in the directory
$target_ldap.
A cross directory move will switch the entry's internal LDAP
reference so updates to the entry will go to the new directory.
If you want to do a cross directory move, you need to pass an
Horde_Ldap_Entry object, otherwise the attributes will be
empty.