Revert "Made the pixel size only computed when changing the coord system or the viewport."

This reverts commit d0fb7009dc5dae77935a96b6b332797d9b7582b3.

The pixel size must be recomputed when the map mode is setting its custom coordinate system
and this is not doing it in all case, breaking randomly the map mode scrolling.

A better overall solution must be found for map mode scrolling.
Fixed the forward thrust length for Bronann.