Card data in images (minimum viable)

* remove wxEmptyString

* improve style tab carousel

* create web request window

* add drop target and drop source

src/data/symbol_font.cpp

@@ -429,7 +429,7 @@ String SymbolFont::insertSymbolCode(int menu_id) const {
   if (insert_symbol_menu) {
     return insert_symbol_menu->getCode(menu_id - ID_INSERT_SYMBOL_MENU_MIN, *this);
   } else {
-    return wxEmptyString;
+    return _("");
   }
 }
 
@@ -505,7 +505,7 @@ wxMenuItem* InsertSymbolMenu::makeMenuItem(wxMenu* parent, int first_id, SymbolF
   }
   if (type == Type::SUBMENU) {
     wxMenuItem* item = new wxMenuItem(parent, wxID_ANY, label,
-                                      wxEmptyString, wxITEM_NORMAL,
+                                      _(""), wxITEM_NORMAL,
                                       makeMenu(first_id, font));
     item->SetBitmap(wxNullBitmap);
     return item;