Validate the monster name letter input form.

Can only enter a single capital letter.
Fixed an issue where the loading overlay would not cover the entire screen after opening and closing a large modal window
The login screen content now scrolls while the title bar stays pinned
Updated the omniwindow callback function signature according to their docs
Committing some work on the facebook friend picker interface

I kinda got it displaying a list of letters on the right side, and clicking the letter jumps to the corresponding group of names. There's still some issues on the actual hardware. Like when it jumps to the group, it renders some of the screen blank until you manually scroll.