ImGui is now initialized once at startup and shutdown before
terminating. graphics initialization is independent.
Move more imgui stuff into imgui drivers.
switch: set scaling on external screen to 1.4, same as xbox
UI scaling refactoring.
ggpo: support for arcade games using keyboard (totd, luptype) and
mouse/rotary encoders (waiwai drive)
Chat and UI now usable when the keyboard is not set to a maple port.