blt tests

[Nelson Minar]

If you want to test blt, I suggest you run the "barchart" and "graph3"
demos: those work for me, and come closest to exercising the features
Swarm uses.

The "you can configure any component by pressing this button" code
doesn't work for me, btw, it complains about X server security. I
think tk4.0 changed the rules for what's allowed and the BLT demos
haven't caught up. It's neat stuff, but we don't use it for Swarm so
you can safely ignore it.