Initial LDAP support

Crude LDAP support. First you run the nt_user_ldap_sync.pl script to add the users from your ldap to the nictool db. This script will also cleanup any users that can't be found on ldap anymore. Then you can login.
[Affero GPL](http://www.affero.org/oagpl.html)  Basically, no. If it is to be bundled with the rest of the NicTool distribution (with the notable exception of the contrib/ dir, then it needs to remain under the AGPL license. Sorry, that's a condition under which NicTool was released to me (and the community).