Desktop grid

This pull request is an attempt to fix #108. It is not perfect yet, because it is only a workaround, but I wanted to create a pull request in order to be able to keep track of the changes and have a place for suggestions.

With the current changes, you will get a regular grid, if you disable preview thumbnails. Icons with text longer than 20 characters will be truncated, because with the modified settings it would destroy the grid.