Convert to .Net Standard

[TheModMaker]

With the new .Net Core, we can run the library on non-Windows platforms without requiring mono. We should upgrade the library to use the new system and to allow building on Linux/Mac.

This will involve removing the portable library and squashing ModMaker.Lua.Net.dll into ModMaker.Lua.dll. Apparently no one wants to have portable library support (see discussion).

[TheModMaker]

03e4947 is part of this change.

[TheModMaker]

See: https://blogs.msdn.microsoft.com/dotnet/2016/09/26/introducing-net-standard/

.Net Core is the new replacement for .Net Framework. It is a cross-platform desktop framework. Using .Net Core doesn't allow it to run on other non-desktop platforms such as Windows Universal Platform.

The other new .Net technology is .Net Standard. This is a replacement for the Portable libraries. It allows a library to target a specific set of APIs and new platforms that are added can implicitly support it. This is what we should be targeting.

However, there are a number of APIs that are not available until recent versions of .Net Standard. For example, System.Threading.Thread isn't available until version 2.0, which is in early access now. In order to support all the features we want, we would have to use 2.0, which can only be compiled using Visual Studio 2017 RC (early access).

As a result, I am deferring this until later.