Handling of view angles is a little hacky at the moment, but this gets
the chase camera code and most of the common input code into one place,
which will make cleaning up the camera code much easier.
Id's binding of escape to togglemenu interfered with the hard-coding
(want escape to togglemenu (or console as a fallback) no matter what).
This idea was part of mercury's original design, too.
This allows id1/qw config files, and to a certain extent scripts, to
work with the new binding system. It does highlight just how limited the
original system was (many keys could not bound).
Mouse axis input does not work yet as that needs a little more work to
support +strafe and +mlook.
