ACtl.TAB_ID
			
			
	Constant that holds the ID of the tab the script is running in. 
				
	
		ACtl.TAB_ID						Returns Type: number 
		A non-zero integer if the script is running in a tab. 
						Zero if the script is running in the background.
		
	Example
	Open a URL in the same tab the script is running in or in the #currentTab if the script is running in the background.
	
	if( ACtl.TAB_ID ){
		//If we are running in a tab
		ACtl.openURL('http://example.com', ACtl.TAB_ID) ;
	}else{
		//If we are running in the background
		ACtl.openURL('http://example.com', '#currentTab') ;
	}