Reallow off-target calculation for a range
Reallow off-target calculation for a range

This was inadvertantly disabled by the change to move the off-target
calculation for a single CRISPR to its own button.

This fix also reenables highlighting a range in the genoverse browser
(which had been disabled to support the off-target calculation feature).

htgt/WGE,htgt/WGE,htgt/WGE,htgt/WGE