This is an extension of host input authority that allows switching the
host (who has zero latency) on the fly, at the further expense of
everyone else's latency. This is useful for turn-based games where the
latency of players not on their turn doesn't matter.
To become the so-called golfer, the player simply presses a hotkey.
When the host is the golfer, latency is identical to normal host input
authority.
Reduces the amount of dependencies dragged in by the main window's
header. This also removes MainWindow.h includes elsewhere where they
aren't necessary, reducing the amount of UI files that need to be
recompiled if the main window's header changes.
