Function setOptionDefault
Sets the default value of an option.
If the option has never been set it is set to the value passed
string | 
		$key | 
		the option name | 
mixed | 
		$default | 
		the value to be used as the default | 
Sets the default value of an option.
If the option has never been set it is set to the value passed
string | 
		$key | 
		the option name | 
mixed | 
		$default | 
		the value to be used as the default |