Include support for LDAP authentication to web interface

Adds LDAP authentication support to the NetSUS web appliance.  A section to configure the LDAP connectivity has been added to the Settings screen of the appliance.  All data required for LDAP authentication are stored in the WebadminConfig object.

![image](https://f.cloud.github.com/assets/6528348/2024094/079f64cc-8865-11e3-8a70-57ff4d738988.png)
![image](https://f.cloud.github.com/assets/6528348/2024100/1d0fd6c0-8865-11e3-9abf-225915354440.png)