wxBitmapComboBox contents needs to support both labels and images

[KeyWorksRW]

Description:

wxBitmapComboBox can have both a label and a bitmap for each item. NodeProperty has a NODEPROP_BMP_COMBO_ITEM structure and a as_bmp_combo_items() method to return a vector of these, but we don't have the custome dialog setup to use them. I thought I already had an issue for this, but I can't find it, so adding it here.