Add auto named group generated when dropping a vehicle onto new group button

src/command_type.h

@@ -404,6 +404,7 @@ enum Commands {
 	CMD_DEPOT_MASS_AUTOREPLACE,       ///< force the autoreplace to take action in a given depot
 
 	CMD_CREATE_GROUP,                 ///< create a new group
+	CMD_CREATE_GROUP_AUTO_NAME,       ///< create a new group with an automatically generated name
 	CMD_DELETE_GROUP,                 ///< delete a group
 	CMD_ALTER_GROUP,                  ///< alter a group
 	CMD_CREATE_GROUP_FROM_LIST,       ///< create and rename a new group from a vehicle list