Megastructure District Rework

Adds new/reworked districts to ringworlds, habitats, and ecumenopoleis for several different empire types. NOTE: Mod development is on indefinite hiatus. I am probably not going to continue updating this, but I am leaving it up in case anyone wants to use it as a base for their own mod (a successor or whatever would be fine) or learn from it. Ringworld Districts To reflect the space available on a ringworld, all ringworld districts (called "expanses" now) are BIG. They provide way more jobs and housing, but also cost more. If ecumenopolis districts are the apex of specialized production (as befits a city), then ringworlds are a vast countryside and are geared for different kinds of basic production. Additionally, ringworlds just flat-out lack a district option other kinds of planets have. I figured that since the main feature of a rindworld is being absolutely huge, a district that allows the player to take advantage of this would be good. Normal, Hive, and Machine Empires each get their own version. Residential Expanse "With this much space, there's no reason not to spread out and build plenty of luxurious residences." Non-Gestalt only. +8 Housing. +6 Amenities. +2 Clerks. Infrastructural Expanse "To efficiently utilize the enormous space of the ringworld, decentralized networks of support, shelter, and supply structures are deployed." Machine Intelligence only. +12 Housing. +3 Amenities. +1 Maintenance Drone. Nesting Expanse "This section of the ring is dotted with drone shelters as far as the eye can see... which is quite far on a convex surface." Hive only. +16 Housing. +1 Maintenance Drone. Agriculture Expanse "Vast tracts of the ringworld's near-endless space set aside for cultivation, either through the growing of crops or animal husbandry." +5 Housing. +5 Farmers/Agri-Drones (+7 for Hives). Generator Expanse "Vast tracts of the ringworld's near-endless space set aside for rows of power plants that generate large amounts of energy which can then be used or co