ParameterRefresher: tool for changing parameter controls individually

ParameterRefresher allows objects to set and refresh their own parameter controls without affecting controls set up by others.

It seems like most people may not run into this situation very often, but for me, it’s not rare for a class to have to be able to set up and modify its own parameter controls.

If I’m using multiple of those classes at once, giving each one the ability to call parameter.clear on its own will mess up all the others, so this class is a utility that lets them all play nice with each other.