1st pass at label group widget

I've got a single test sort of working, in that it probably needs tweaking as we look at what it is doing from the labelCalloutTests.html file.

I've started the labelLite method, but stopped because I was thinking that setting up some css would be better than what's currently happening. I've got the code which I expect will add a "lit" class to the requested labels and remove it from all others in the label group.
Completed untested at this point.