Automatically autotile new windows to snap to nearest region

i.e. when I tear off a tab from my browser or open a new window, it should tile to half (configurable) of the screen on whatever screen it opened on

At the moment, I'm still working on the GTK+ 3.x port which slipped behind schedule, but I'll leave this open as a reminder for once that and the more pressing features are done. (eg. moving the definition of the tiling grid into the config file)