This is needed to make sure that all of the buttons get updated - some will
have stale states, otherwise

The last state of the upgrade buttons are now cached. This ensures that
the classList is perturbed *only* if this would actually change the
appearance, and seems to be far faster than just adding something
to the classList over and over

This has broken quite a bit, since many parts of the game expect a scalar instead of
a whole object. I have also been deep freezing constant configuration data and, generally,
trying to make as much immutable as possible