Make all space stations on same Z-level in Space

Different planet’s space stations are now on different Z-levels which means that if you travel between planets (either flying or warping) you need also to ascend or descend Z-lvl to find the space station. It is quite intuitive - and you still need to be somewhat close to a space station in order for it to be visible. Not all planets have landing zones so several need you to go to space station in order to land (e.g. Toulan, Monria, Setesh)