This accomplishes two main things:
- Creates a mapgen_helper.lua module containing functions useful for Lua map generators
- Paves the way for allowing the cave generator to produce scenarios and accept user configuration
This map generator is used in HttT 17 and SoF 4. which needed to be updated aswell.
With this we finally have a lua generator that is used in mainline and that
can be used an an example by wml authors who want to write other map generators.
Unfortunateley there are still umc add ons in 1.12 that use
scenario_generation=cave so i didn't remove the cpp implementation yet.
