WIP: Support multiple-line labels in the icon grid

This fixes the long known issue about ellipsizing search results and items in the app overview. Also includes a fix for the missing spacing between icons and labels.

I know this is not very neat and more like a big hack, but this issue is so annoying to everybody I'd like to have it merged anyway. The icon grid wasn't designed with flexibility in mind and has fixed widths and heights for the items defined in css, on top of that it's slow, inefficient and a pain to work with. In my opinion it's not worth investing more time and should be rewritten from scratch (probably together with AppDisplay and parts of the search).