Links many map-specific details such as the station name, z-level information, and allowed jobs from global vars to map datum vars, which should help us maintain multiple maps at once in the future, which will be needed for the future Southern Cross.
Note that a config change will be needed to change GENERATE_ASTEROID to GENERATE_MAP, otherwise no changes should be required to continue normal map usage.
To change to a different map, it's suggested to tick the file that ticks all the other needed files, which for the Northern Star is called northern_star.dm.
It will first check to see if the turf is set, and if not it will still use the z-level default.
This means we can mark areas as having a base of space to override the z-level base of asteroid that we're using.
As a result, we can ensure the bombs, shuttles moving, etc. leave behind an space turf by defining shuttles, solars/"external" areas as using space as a base.
Areas will need to be updated to check with base_turf = /turf/space and references to the old get_base_turf proc updated so all calls (bombs, Nar'Sie, deconstruction, etc.) have the correct effect, but it's tired and I want to commit this now so I'm committed to finishing it tomorrow.
Created a global list to track base turfs for explosions/shuttle moves.
Remaps the asteroid to be a moonlet. Tidies up some references to 'asteroid', removes moonbase from the accessible z level list.
