WorksheetStyle.ShouldFreezeTopRow not general enough

[jzabroski]

Not clear how it interacts with HeaderIndexRow property.

Problems arise when you have multi-row headers, such as when the first header row is used to span three columns of text to avoid repeating text in each column, such as "Total" top row span of "Cost | Profit"

[folkcoder]

This should be addressed by v1.2.1. Note that ShouldFreezeTopRow has been renamed to ShouldFreezeHeaderRow in order to better signal the setting's intent.