Multisite Version

Hi Clifton, 

We're using your Simple LDAP Login plugin at the university I work at. We use multisite installations and need the authentication to work across the entire WordPress installation and make changes to the settings in one location – in the network admin. I made the following changes in this branch.

When the plugin is network activated...
* Store and retrieve all settings from network options instead of the site-level options
* Show the option page under Network admin > Settings > Simple LDAP Login

Your plugin has been great, thank you for it! We've been using it in production with these changes for 6 months or more, and I just wanted to share our changes back with the community.

What do you think?