[PATCH] Don't allow editing time fields when All day is set

When All day [ ] is checked at http://demo.wp-events-plugin.com/submit-your-event/, the time fields are still editable both manually and through timePicker. They also look that way.

Suggested changes:

1. Prevent manual editing by setting fields readonly when All day [ ] is checked:

   $('input#em-time-all-day').change(function(){
   	if( $('input#em-time-all-day').attr('checked') ){
   		$('.em-time-input').attr('readonly', true);
   	}else{
   		$('.em-time-input').attr('readonly', false);
   	}
   });

2. When the fields are readonly, make it be evident to user. I think this part of events-manager.js is attempting that, but doesn’t get called when All day [ ] is changed:

   //Sort out all day checkbox
   wrap.find('.em-time-range input.em-time-all-day').change(function(){
   	var allday = jQuery(this);
   	if( allday.is(':checked') ){
   		allday.siblings('.em-time-input').css('background-color','#ccc');
   	}else{
   		allday.siblings('.em-time-input').css('background-color','#fff');
   	}
   }).trigger('change');

   This should be easy to merge with the patch in #1.

3. Disable timePicker for both fields while they are readonly.

http://wordpress.org/extend/plugins/events-manager/