Multisite support

Hi,

Fisrt of all, thank you very much for your plugin.

I would be wonderful if your plugin can be used in WP Multisite context, with network-activated.
For example, sometimes i would perform maintenance operations but i would keep all front-end blogs accessible. So i would disable login for all users but only from network admin panel. Not blog by blog on each blog admin panel.

So the i would disable login for all blogs from network admin panel.

Best regards.