Auto Generation of squad and sortie units

As the title says, everything to do with sorties and squads is now moved to the defs in LuaRules/Configs.
The unitdefs themselves are generated in gamedata/unitdefs_autogen.lua

The first two commits are other refactors which might be nice.
Be sure to merge https://github.com/spring1944/additional-sides/pull/1 if you merge this one.