Set the FlexGrid's selectionMode property to MultiRange to enable
Excel-style multi-range selection.
Users will be able to select multiple ranges by ctrl-clicking and dragging
on the grid.
The selectedRanges property gets an array containing CellRange
objects that contain the currently selected ranges.
The sample shows how you can provide Excel-style dynamic data summaries
for the current selection (regular or multi-range).
It also shows how you can export selected ranges to CSV files.
Note that clipboard and export commands only work for multi-range selections
if all selected ranges refer to the same column range or to the same row range.
(Excel also behaves this way.)