Initial WZ 4.5.0+ adjustments

[past-due]

Including support for the new Campaign Mod Packaging

• Add GPL-2.0-or-later licensing information (as discussed on Discord)
• Add mod-info.json
• Remove all other (base override) campaign json (no longer needed)
• Simplify gamedesc.lev (no longer needs anything but Reclamation levels)
• Remove some unused base files (for fastplay and tutorial)
• Update README.md with WZ 4.5.0+ campaign mod instructions
• Update audio.cfg to json format, use a separate file for just the overrides for this mod (WZ 4.5.0+)

NOTE: To test, needs a WZ master branch build that is https://github.com/Warzone2100/warzone2100/commit/39b0138c6b4a24a1d411e59f310dacd9860cee44 or later

Once you have a new-enough master branch build of WZ, package the contents of the repo into a .wz file and then install the .wz file in mods/campaign (not autoload). This will enable it to work with the new campaign selector UI.

Possible future TODO (left for a later PR):

• Review recent upstream WZ script changes in https://github.com/Warzone2100/warzone2100/commits/master/data/base/script, starting at https://github.com/Warzone2100/warzone2100/commit/007b31e2e7759511b9e6e296f57a6d6dfbe491f6 - port whatever is desired
  • Example: Core WZ now has handling for artifact recovery that may be desirable to adopt?