Making a button that will allow multiple blocks to be selected.
Meant to calculate totals for multiple blocks selections, but this is selecting multiple tracts and showing the stats for the aggregate tracts.  Also clear selection doesn't work.
Fixed some errors with button names, next fix block selections.
something is wrong with tract highlighting, looking for dupes in selected blocks doesn't work yet.
Multiple selection is sort of working, but clicking on already clicked on blocks makes them not get highlighted.
Now can select multiple blocks fine without previous glitch, need to restore tract visual
Now tract visual is showing up correctly again.  Next to corner points to define a box selection.