Application Scaling for MSW: Next big step

- Added rescale() function for the most of controls
 - Created PrusaBitmap and PrusaButton classes like a wrap to wxBitmap and wxButton accordingly

src/slic3r/GUI/GUI_App.hpp

@@ -98,6 +98,7 @@ public:
     void            init_label_colours();
     void            update_label_colours_from_appconfig();
     void            init_fonts();
+    void            scale_fonts(const float scale_f);
     void            set_label_clr_modified(const wxColour& clr);
     void            set_label_clr_sys(const wxColour& clr);