add orderlist export/import buttons

src/lang/extra/english.txt

@@ -1681,6 +1681,8 @@ STR_ORDER_REVERSE_ORDER_LIST                                    :Reverse order l
 STR_ORDER_APPEND_REVERSED_ORDER_LIST                            :Append reversed order list
 STR_ORDER_DUPLICATE_ORDER                                       :Duplicate order
 STR_ORDER_CHANGE_JUMP_TARGET                                    :Change jump target
+STR_ORDER_EXPORT_ORDER_LIST										:Copy order list to file
+STR_ORDER_IMPORT_ORDER_LIST										:Get order list from file
 
 STR_ORDER_TRY_ACQUIRE_SLOT_BUTTON                               :Try acquire slot
 STR_ORDER_RELEASE_SLOT_BUTTON                                   :Release slot

src/order_gui.cpp

@@ -633,6 +633,8 @@ enum OrderDropDownID {
 static const StringID _order_manage_list_dropdown[] = {
 	STR_ORDER_REVERSE_ORDER_LIST,
 	STR_ORDER_APPEND_REVERSED_ORDER_LIST,
+	STR_ORDER_EXPORT_ORDER_LIST,
+	STR_ORDER_IMPORT_ORDER_LIST,
 	INVALID_STRING_ID
 };
 
@@ -3488,6 +3490,8 @@ public:
 				switch (index) {
 					case 0: this->OrderClick_ReverseOrderList(0); break;
 					case 1: this->OrderClick_ReverseOrderList(1); break;
+					case 2: /*TODO:Copy order list as Unified Order List Format*/break;
+					case 3: /*TODO:Pase order list as Unified Order List Format*/break;
 					default: NOT_REACHED();
 				}
 				break;