Add wxAddRemoveCtrl

[KeyWorksRW]

Description:

wxAddRemoveCtrl -- https://docs.wxwidgets.org/trunk/classwx_add_remove_ctrl.html

We should be able to at least add a listbox version of this. For the four functions, we could use code snippets -- edited and saved similar to what we use for lambdas. The derived class would use the base class name as the prefix to make it unique, and would be defined in the source file where the wxAddRemoveCtrl is created.

[KeyWorksRW]

This could be done by having a property for the class name, and a property for the type of control to hook it up to. We could then declare the class at the end of the class header file unless the user didn't want a closing brace (in which case it would go at the top). We could then add comments just before the end of the comment block showing the functions that must be defined.

Note that wxPython and wxRuby3 do not support this control.

While doable, I wonder if it would just end up being confusing -- it requires the user to create the class definitions somewhere. That's not going to be immediately obvious, and the dev's program won't link until those 4 functions are defined.