Add a readme file with the thirdparty dll sources.

Closes #6863.
Merge pull request #6972 from pchote/thirdparty-readme

Closes #6863
remove lonely tab
port gdi03 to the new Lua API
fix harvesters crushing the sand bags
let nod attack from different directions
Merge pull request #6795 from Mailaender/gdi03-new-lua

Ported mission GDI03 to the new Lua API
Implementation of the automated D2k Carryall

Closes #2246
Add myself to Authors
Style fixes
Extract an interface for Harvester <-> carryall communication.