Load new tiles in the correct position

`MM.moveElement` in `MM.Layer.positionTile()` did not take account of the scale when setting the tile position. This is a problem when loading new tiles at non-integer zooms: tiles load first out of position, and then "jump" to the correct position when `MM.Layer.adjustVisibleLevel()` is called (which correctly includes the scale in the position calculation for `MM.moveElement`).

This change basically makes the `MM.moveElement` call in `MM.Layer.positionTile()` the same as that in `MM.Layer.adjustVisibleLevel()`. Makes for a much smoother experience when using the [easey library](https://www.mapbox.com/easey/) and zooming the map.