Improve resolution selection in Launcher

In 0.48 it looks like this:

Known issues:

1. Tab characters between resolutuon text and aspect ratio text do not allow widget to resize properly. They should be replaced to spaces.
2. Only left column on the Display tab grown when you resize the Launcher.
3. GCD should not be always used to determine aspect ratio. We handle only one such case (8:5 is displayed as 16:10), but there are other cases.
4. We do not display aspect ratio when we fail to classify the resolution (e.g. for 5:4 resolutions).
5. Classification is really weird - it handles only 16:9, 16:10 and 4:3 aspect ratios, when there are plenty other ones.
6. Launcher and OpenMW use different code to format resolution, so we have a code duplication.