Review pixel alignment for TileLayer

[oliverheilig]

One could expect that the pixels of an image-tile exeactly match the pixels on the panel if:

• Windows is confiugured in a way that corresponds to a 96-DPI resolution for the panel.
• The map is zoomed at an integer zoom-level
• The (WPF-) container of the map is aligned to pixels (UseLayoutRounding=true)

Note: This isn't easy to implement. Unlinke the NonTiledLayer, which is always aligned exactly to the viewport-rect, the tiles can have any wpf position (Pan-Transformation X/Y). This would require a "pan snapping", so the texture-pixel exactly hits the panel-pixel for this case.