Multiple whole row/column selections deleted upon hover over the tree of that dimension

[Robert Leach]

1. Select multiple rows with click & shift-click or command-click.
2. Hover over the row tree.

Result: all selected rows get collapsed down to a single row selection.

[Robert Leach]

Resolved issue #216. Hovering over the trees after selecting multiple rows/columns now no longer deselects all but 1 row/col.

The code had originally been written to only handle 1 whole row/col being selected. I uncommented a find nearest node function, then added some checks to ensure the selection was contiguous.

→ <<cset 57e6bf1d5365>>

[Robert Leach]

This is now fixed. The code for determining which tree node is currently selected was originally written to only handle a single row/col. Now it can handle multiple. Only contiguous selections will trigger a tree selection.

[Robert Leach]

Merged to master.