Legacy support

While tkinter widgets are not the focus of the library, I applied some default styling for each theme to legacy widgets so that they didn't stick out. A large reason for this is that several ttk widgets use tkinter widget components under the hood. So it was necessary to style these as well so that, for example, the popdown list in the Combobox, or the Menu in the menubutton are styled appropriate.

Below are examples of a light and dark themes using legacy tkinter widgets.