[Alt-Tab] When activated on an empty workspace, don't default-select any window at all.
[Alt-Tab] Enable multi-line title labels.
[Alt-Tab] Avoid different icon heights when scrolling through the icons.

Since the selected icon may have a different style than the rest, it's
bad to have that icon be the model for all icons.
[Alt-Tab] Size allocation is smoother if 'squareItems' is false.
[Alt-Tab] Add PageUp- and PageDown- sensitivity.