Trace UI Performance Improvements.
The PackageList was taking too long to set up. It turned out the Bacon.combineTemplate streams were eating up multiple seconds (each) to initialize. Added a "SetProp" to create roughly the same functionality, and it seems to be significantly more efficient. (A dataset with 2000 packages went from an 8-10 second load time to a 3-4 second load time)
I also had to make a couple of modifications in traces.js since the selection states were converted from Map[id->boolean] to Set[id].