Add support for multinetwork SSO

[hajekj]

Since the "correct" way (according to John James Jacoby) to run multiple domains in WordPress is using the WP Multi Network plugin, it would be great if this plugin also had an option for multi network SSO.

[danieliser]

Gotta say that this would be awesome, I know @johnjamesjacoby said one was in the works, though I can't find any sign of it yet. Hope this can happen :)

[smccafferty]

While I haven't had much time to add functionality lately this does look interesting and something I will look into adding.