=== to add a new widget ===


=== to add a new widget option ===
- add a new variable		<widget_option.h>
- to initialize the variable, modify _wod_init()		<widget_option.c>
- add a new entry in widget_option_content_update()		<widget_option.c>
	ex) WIDGET_OPTION(notify, ETV_ID_NOTIFY)
- add specific options		<widget_option.c>
	- check
		- for caller
			WIDGET_OPTION_CHECK_ADD("Allow background events", wod->notify_event, _notify_event_changed_cb);
		- for callee
			WIDGET_OPTION_CHECK_CHANGED_CB(notify_event, wod->notify_event);
- use specific options		<widget.c>
	if (wod)
		{
			if (wod->btn_text)
				elm_object_text_set(o, "This is a Button");
		}