Update classref and docs, fix missing parameters' name

doc/classes/OptionButton.xml

@@ -198,6 +198,7 @@
 			<argument index="0" name="ID" type="int">
 			</argument>
 			<description>
+				This signal is emitted when user navigated to an item using [code]ui_up[/code] or [code]ui_down[/code] action. ID of the item selected is passed as argument (if no IDs were added, ID will be just the item index).
 			</description>
 		</signal>
 		<signal name="item_selected">