[Alt-Tab] Scroll icon list earlier when we are approaching the edge (7).
[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.