selecting a style in the styles dialog ( without double clicking )
will apply the style to the currently selected cell(s) You can
with the keys navigate to other styles and they in turn will
also be applied. Preview will end when you click back onto the
document.

*FIXME* - the styles dialog isn't really suitable for previewing, a
new dialog ( possibly in the toolbar ) might be nicer ( see Excel )

*FIXME* - when there is a multiple selection the highlight colour
(applied as a transparent overlay) is most annoying ( and is mixed
with any background colour applied if part of a style )
see ( ScGridWindow::UpdateSelectionOverlay() ) However my puny
attempts to make the selection use a transparent colour made all the
borders of the selected cells dissappear. I guess maybe a box/border
 around each selected cell ( or group of cells ) would also work
but I didn't try that

Change-Id: I0950e79085ffb75f60ee961835665df0c230172f