WIP Work/jriddell/wallpaper title

Set text to one line only, otherwise it overspils because the elide (ellipsis) does not seem to work.

There is probably a better fix for this here so this is pushed mostly for my own interest frameworks/kcmutils!244 (merged)

It crashes on close because the string is made on the local stack and my c++ is too rusty to remember how to fix that