LDAP Settings model

[ajeygore]

When system comes up first time, we should have a LDAPServer model in the system with a view, if this model does not exist then system should present ldap server setup view with following parameters

1. ldap server host
2. ldap server port
3. ldap server dn
4. ldap server search base
5. email address field
6. ssh public key field
7. hachi_admin username - comma separated
8. ldap_admin username
9. ldap_admin password