* Added a proc to the map datum which returns what zlevels a nanomap capable computer should display.
* Updated the atmos control, power monitoring, crew monitoring, and camera consoles to use it.
* Changed templates to not show the map button if no map levels are available.
* Settings for specific z-levels are defined in datum types, allowing the lists of Z levels to be automatically configured. This solves the problem of being unable to use the z-level #defines in associative lists.
* Converted the example and northern star maps to use the new system.
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.
