Windows compile fixes

[ahockersten]

• Makes sure the code can be compiled on Windows
• Adds build instructions for Windows
• Fixes some other various issues related to building
• Adds a .gitignore file

Some issues that this has:

• I have not tested it on MacOS, so it's possible it breaks MacOS building
• You now need to copy Assembly-CSharp.dll, UnityEngine.dll and JsonFx.dll to the root of the repo folder.
• The Scrollsmodloader.interfaces.dll file is no longer referenced. Instead the project is referenced directly. That means the GameReplay.mod cannot be compiled, since it has not been updated to use the new interfaces. I have not tried fixing this.