In kde4 times, the layout of clock's tooltip was nicely arranged using a
table. Now it's a bit of a mess so this brings back some nice layout.

Also simplifies the timeForZone function which is used only for the
tooltip.

BUG: 357005
BUG: 351472
CCBUG: 357004
FIXED-IN: 5.6.0
REVIEW: 124047