Only set width or height minima, so the systray expands only in the expandable direction. minimum width and height are 22 in those cases.

This patch makes it possible to shrink the systray - and with it the whole panel - again, once it has had more rows. This wasn't possible after <a href="http://websvn.kde.org/?rev=826397">r826397</a>;.

This makes the whole panel not shrink below 22.

If we make that possible (by not setting the min height to 22), the systray just vanishes when the panel gets smaller.

Not sure which situation I prefer, ideas?