showMenu() pass a variable into click handlers

I needed showMenu to be able to support having a variable passed into it so that the click handlers could use the variable. In my case I'm going to pass the dom element clicked on when showMenu() is called so one of the items in the context menu can delete that clicked dom element. 

I just copied the way you had the arguments for message payload from one of the other functions. 


Also unrelated... a set of quotes around the build path in the script that is run will prevent errors due to spaces in the ${SRCROOT}/public folder.