Added ability to work by HTML ID attribute

Hey Chris.  Liking Ji a lot so far.  It's easier for beginners like me to set up and get going quickly than, say, Fay and Snap and a proper web service, especially since my app is meant for desktop for the time being.

I needed to be able to retrieve HTML elements by id, so I added a few utility methods for working with ids.  I saw that the client side JS assigns elements an ID when generating lookup keys client side, so I changed that to an elid property to not clobber the id's I'm setting intentionally.  Been using various iterations of this for a couple days and they seem to work without incident.  

Note that I am getting "no element found" exceptions on FF but not chrome.  I don't know whether this is a result of my changes or not, but it seems to have no effect.  FYI, the FF web console indicates the error occurs on line 1 of "signal."  I haven't been able to track it down.

Thanks,
Dan