Improve scaling to different resolutions

[Linus4]

Currently we use renderer.SetLogicalSize() in app.go to support resizing the window. The logical size we use suits 1080p displays. When resizing the window (especially when scaling it down) problems with the ttf and gfx drawings occur because some drawings are thinner than a single pixel (at least that's what I think).

Font becomes illegible, some lines and circles are drawn poorly and there are weird lines in smokes and mollys.